A pretreatment method for wastewater generated in the preparation of 1,2-pentanediol by oxidation of n-pentene

Abstract

The present application belongs to the field of fine chemical wastewater treatment, and particularly relates to a pretreatment method of wastewater generated in preparation of 1,2-pentanediol by n-pentene oxidation method. The activated carbon loaded peroxymolybdophosphoric acid quaternary ammonium salt catalyst is added into the wastewater to be treated, and ultraviolet light irradiation is carried out, and hydrogen peroxide is added to react, so as to degrade 1,2-pentanediol in the wastewater and remove COD, and then the pretreatment of the wastewater is realized. The activated carbon loaded peroxymolybdophosphoric acid quaternary ammonium salt catalyst can promote the hydrogen peroxide oxidation reaction, and can also degrade 1,2-pentanediol, and the amount of hydrogen peroxide can be reduced.

Description

Technical Field

[0001] The present invention belongs to the field of fine chemical wastewater treatment, and specifically relates to a pretreatment method for wastewater generated by the n-pentene oxidation process to prepare 1,2-pentanediol. Background Art

[0002] 1,2-Pentanediol is a colorless and odorless liquid and an important intermediate of the fungicide propiconazole. At the same time, due to its excellent moisturizing and antiseptic properties, it is also widely used in cosmetics.

[0003] There are multiple existing methods for producing 1,2-pentanediol. These methods are categorized by the starting raw materials: the n-pentene method, the furfural or furfuryl alcohol method, the n-pentanoic acid method, the n-butyraldehyde method, and the n-butanol method. The n-pentene method involves reacting the raw material with hydrogen peroxide to form an epoxide, which is then hydrolyzed and ring-opened under acidic or alkaline conditions to produce the final product, 1,2-pentanediol. However, the n-pentene oxidation method for producing 1,2-pentanediol produces a large amount of wastewater. Direct discharge of this wastewater without proper treatment can cause serious environmental pollution. Among traditional wastewater treatment methods, biological methods are widely used due to their economical and environmentally friendly properties. However, biological methods face significant challenges in treating 1,2-pentanediol production wastewater. This is primarily because 1,2-pentanediol, as the primary organic component in wastewater, exhibits strong toxicity to microorganisms. This toxicity not only inhibits microbial activity but also significantly reduces the efficiency of biological treatment systems. Even when diluting the wastewater to reduce the 1,2-pentanediol concentration, the biochemical treatment effect remains unsatisfactory and fails to meet relevant environmental standards and requirements. Therefore, direct biological treatment of 1,2-pentanediol production wastewater is clearly not a viable solution. Prior to biological treatment, it is crucial to perform necessary pretreatment of the wastewater. The purpose of pretreatment is to reduce the concentration of 1,2-pentanediol in the wastewater or modify its form, thereby mitigating its toxic effects on microorganisms and improving the efficiency and effectiveness of subsequent biological treatment.

[0004] Therefore, in order to treat the wastewater produced by 1,2-pentanediol, developing an effective pretreatment technology to overcome the limitations of existing biological treatment methods is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings, the present invention provides a pretreatment method for wastewater produced by the n-pentene oxidation process to prepare 1,2-pentanediol. The method of the present invention can effectively treat 1,2-pentanediol in the wastewater, avoid the inhibition of 1,2-pentanediol in the wastewater on microorganisms in the biochemical treatment tank, and improve the biodegradability of the wastewater.

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

[0007] Activated carbon-supported quaternary ammonium peroxymolybdate catalyst is added to the wastewater to be treated, and ultraviolet light is irradiated. At the same time, hydrogen peroxide is added to react to degrade 1,2-pentanediol in the wastewater and remove COD, thereby achieving pretreatment of the wastewater.

[0008] Specifically, activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst is added to the wastewater to be treated, ultraviolet light is irradiated at 60-70° C., and hydrogen peroxide is added to react for 1.5-2.5 hours.

[0009] The amount of the catalyst used is 0.08-0.2% w / w of the mass of the wastewater to be treated, and the amount of the hydrogen peroxide used is 0.25-0.4% w / w of the mass of the wastewater to be treated.

[0010] Preferably, the amount of catalyst used is 0.1% w / w of the mass of wastewater, the amount of hydrogen peroxide used is 0.3% w / w of the mass of wastewater, the reaction temperature is 65° C., and the reaction time is 2.0 h.

[0011] The activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst is prepared by dripping a peroxyphosphomolybdic acid solution into a benzyltriethylammonium chloride ethanol solution, stirring the solution at a constant temperature, cooling the solution, standing the solution, and drying the solution. The peroxyphosphomolybdic acid solution is obtained by dissolving the phosphomolybdic acid in distilled water and reacting the solution with 30% w / w hydrogen peroxide. The benzyltriethylammonium chloride is added to ethanol and dissolved, and the activated carbon is added to obtain a solution.

[0012] The insulation temperature is 70-78°C, the insulation stirring time is 4-8 hours, the temperature is lowered to 15-25°C, and it is allowed to stand for 12-24 hours. The drying temperature is 110-130°C, and the drying time is 7-9 hours.

[0013] Preferably, the insulation temperature is 78° C., the insulation stirring time is 6 hours, the temperature is lowered to 20° C., and the mixture is allowed to stand for 18 hours. The drying temperature is 120° C., and the drying time is 8 hours.

[0014] The amount of distilled water used is 8 to 12 times the mass of phosphomolybdic acid w / w, and the amount of hydrogen peroxide used is 1.3 to 1.7 times the mass of phosphomolybdic acid w / w;

[0015] The amount of benzyltriethylammonium chloride used is 1.1 to 1.3 times the mass of phosphomolybdic acid (w / w), the amount of ethanol used is 8 to 12 times the mass of benzyltriethylammonium chloride (w / w), and the amount of activated carbon used is 3.5 to 4.5 times the mass of phosphomolybdic acid (w / w).

[0016] Preferably, the amount of distilled water is 10 times the mass of phosphomolybdic acid, the amount of hydrogen peroxide is 1.5 times the mass of phosphomolybdic acid, the amount of benzyltriethylammonium chloride is 1.2 times the mass of phosphomolybdic acid, the amount of ethanol is 10 times the mass of benzyltriethylammonium chloride, and the amount of activated carbon is 4.0 times the mass of phosphomolybdic acid.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The active carbon supported quaternary ammonium peroxymolybdophosphate catalyst used in the present application not only greatly promotes the hydrogen peroxide oxidation reaction, but also has a good photocatalytic effect on the ultraviolet light degradation of 1,2-pentanediol, thereby reducing the amount of hydrogen peroxide.

[0019] 2. The 1,2-pentanediol in the present application is subjected to free radical oxidation under the conditions of hydrogen peroxide and ultraviolet light, and the 1,2-pentanediol is oxidatively degraded into products such as organic acids or carbon dioxide, and the degradation products have no microbial inhibitory effect, and can be used for biochemical treatment.

[0020] 3. The active carbon supported quaternary ammonium peroxymolybdophosphate catalyst in the present application has high oxidation catalytic activity and ultraviolet light photocatalytic activity, and can effectively remove residual 1,2-pentanediol in wastewater.

[0021] 4. The COD removal rate of the method in the present application is above 80%, which not only solves the activity inhibition of 1,2-pentanediol on microorganisms, but also reduces the organic matter content of wastewater and improves the biodegradability of wastewater.

[0022] 5. The method in the present application is simple in operation, low in cost, and has a wide commercial application prospect. DETAILED DESCRIPTION

[0023] The present application will be further explained through specific examples.

[0024] The wastewater to be treated comes from the production process of preparing 1,2-pentanediol by using n-pentene as a raw material, wherein the main components of the wastewater are water and a small amount of 1,2-pentanediol entrained by azeotropic, and the COD of the wastewater is about 2000 mg / kg, and the content of 1,2-pentanediol is 0.09%.

[0025] Example 1

[0026] Preparation of the active carbon supported quaternary ammonium peroxymolybdophosphate catalyst:

[0027] 1. Preparation of peroxymolybdophosphoric acid solution: 10.0 g of phosphomolybdic acid was placed in a beaker, 100 g of distilled water was added and stirred to ensure that the phosphomolybdic acid was completely dissolved, then 15.0 g of 30% hydrogen peroxide was added, and stirred at room temperature for 15 min to obtain a peroxymolybdophosphoric acid solution.

[0028] 2. Preparation of benzyltriethylammonium chloride ethanol solution: 12.0 g of benzyltriethylammonium chloride was placed in a three-necked flask, 120 g of ethanol was added and stirred to dissolve, then 40.0 g of activated carbon was added to obtain a benzyltriethylammonium chloride ethanol solution.

[0029] 3. Synthesis of catalyst: At room temperature, add peroxyphosphomolybdic acid solution dropwise to benzyltriethylammonium chloride ethanol solution, raise the temperature to 78°C, maintain micro-reflux, and continue stirring at this temperature for 6 hours, then cool to 20°C, let stand for 18 hours, and filter to separate the filter cake. Rinse the filter cake with water and ethanol respectively to remove impurities attached to the surface of the filter cake. Dry the washed filter cake in a 120°C forced air drying oven for 8 hours to obtain the catalyst.

[0030] Example 2

[0031] Preparation of activated carbon-supported quaternary ammonium peroxymolybdate catalyst:

[0032] 1. Prepare peroxyphosphomolybdic acid solution: Take 10.0g of phosphomolybdic acid and place it in a beaker. Add 80g of distilled water and stir thoroughly to ensure that the phosphomolybdic acid is completely dissolved. Then add 13.0g of 30% hydrogen peroxide and stir at room temperature for 15 minutes to obtain peroxyphosphomolybdic acid solution.

[0033] 2. Prepare benzyltriethylammonium chloride ethanol solution: Take 11.0g of benzyltriethylammonium chloride, place it in a three-necked flask, add 132g of ethanol, stir to dissolve, and then add 45.0g of activated carbon to obtain benzyltriethylammonium chloride ethanol solution.

[0034] 3. Synthesis of catalyst: At room temperature, add peroxyphosphomolybdic acid solution dropwise to benzyltriethylammonium chloride ethanol solution, raise the temperature to 75°C, maintain micro-reflux, and continue stirring at this temperature for 8 hours, then cool to 25°C, let stand for 24 hours, and filter to separate the filter cake. Rinse the filter cake with water and ethanol respectively to remove impurities attached to the surface of the filter cake. Dry the washed filter cake in a 130°C forced air drying oven for 7 hours to obtain the catalyst.

[0035] Example 3

[0036] Preparation of activated carbon-supported quaternary ammonium peroxymolybdate catalyst:

[0037] 1. Prepare peroxyphosphomolybdic acid solution: Take 10.0g of phosphomolybdic acid, place it in a beaker, add 120g of distilled water and stir thoroughly to ensure that the phosphomolybdic acid is completely dissolved, then add 17.0g of 30% hydrogen peroxide and stir at room temperature for 15 minutes to obtain peroxyphosphomolybdic acid solution.

[0038] 2. Prepare benzyltriethylammonium chloride ethanol solution: Take 13.0g of benzyltriethylammonium chloride, place it in a three-necked flask, add 104g of ethanol, stir to dissolve, and then add 35.0g of activated carbon to obtain benzyltriethylammonium chloride ethanol solution.

[0039] 3. Synthesis of catalyst: At room temperature, add peroxyphosphomolybdic acid solution dropwise to benzyltriethylammonium chloride ethanol solution, raise the temperature to 76°C, maintain micro-reflux, and continue stirring at this temperature for 4 hours, then cool to 15°C, let stand for 12 hours, and filter to separate the filter cake. Rinse the filter cake with water and ethanol respectively to remove impurities attached to the surface of the filter cake. Dry the washed filter cake in a 110°C forced air drying oven for 9 hours to obtain the catalyst.

[0040] Example 4

[0041] 500 g of the 1,2-pentanediol production wastewater to be treated was placed in a 1 L beaker, 0.5 g of the catalyst prepared in Example 1 was added, the mixture was stirred and heated to 65° C., 1.5 g of 30% hydrogen peroxide was added dropwise under ultraviolet irradiation, and the reaction was continued for 2 h. The temperature was then lowered, the catalyst was filtered out, and the COD of the filtrate was detected.

[0042] The treatment effect is: the COD removal rate of the pretreated wastewater is 90%, the 1,2-pentanediol content is 0.009%, and the pretreated 1,2-pentanediol wastewater is suitable for treatment by microbial treatment method to meet the standards.

[0043] Example 5

[0044] 500 g of 1,2-pentanediol production wastewater was placed in a 1 L beaker, 0.4 g of the catalyst prepared in Example 2 was added, the mixture was stirred and heated to 60° C. 2.0 g of 30% hydrogen peroxide was added dropwise under ultraviolet irradiation, and the reaction was continued for 2.5 h. The temperature was then lowered, the catalyst was filtered out, and the COD of the filtrate was detected.

[0045] The treatment effect is: COD removal rate is 86%, 1,2-pentanediol content is 0.0126%, and the 1,2-pentanediol wastewater after pretreatment is suitable for microbial treatment to meet the treatment standards.

[0046] Example 6

[0047] 500 g of 1,2-pentanediol production wastewater was placed in a 1 L beaker, 1.0 g of the catalyst prepared in Example 2 was added, the mixture was stirred and heated to 70° C. 1.25 g of 30% hydrogen peroxide was added dropwise under ultraviolet irradiation, and the reaction was continued for 1.5 h. The temperature was then lowered, the catalyst was filtered out, and the COD of the filtrate was detected.

[0048] The treatment effect is: COD removal rate is 91%, 1,2-pentanediol content is 0.0081%, and the 1,2-pentanediol wastewater after pretreatment is suitable for treatment by microbial treatment method to meet the treatment standards.

[0049] Comparative Example 1

[0050] The difference from Example 4 is that the catalyst uses phosphomolybdic acid, and other conditions are the same as in Example 4, specifically:

[0051] Take 1,2-pentanediol production wastewater 500 g in a 1 L beaker, add catalyst phosphomolybdic acid 0.5 g, stir to 65 ℃, add 30% hydrogen peroxide 20 g under UV irradiation, continue to react for 2 h, cool, filter out the catalyst, and detect the COD of the filtrate.

[0052] The treatment effect is: the COD removal rate is 11%, the content of 1,2-pentanediol is 0.08%, and the pretreated wastewater cannot be used for subsequent microbial biochemical treatment.

[0053] Comparative Example 2

[0054] The difference between Example 4 and Example 4 is the preparation method of the activated carbon supported peroxo phosphomolybdate quaternary ammonium salt catalyst, and the other conditions are the same as Example 4, which are as follows:

[0055] 1. Preparation of peroxo phosphomolybdate solution: take 10.0 g of phosphomolybdate and place it in a beaker, add 100 g of distilled water and stir well to ensure that the phosphomolybdate is completely dissolved, then add 15.0 g of 30% hydrogen peroxide, stir at room temperature for 15 min, and obtain the peroxo phosphomolybdate solution.

[0056] 2. Preparation of cetyltrimethylammonium chloride ethanol: take 17.3 g of cetyltrimethylammonium chloride and place it in a three-necked flask, add 120 g of ethanol and stir to dissolve, then add 40.0 g of activated carbon to obtain a cetyltrimethylammonium chloride ethanol solution.

[0057] 3. Synthesis of catalyst: at room temperature, add the peroxo phosphomolybdate solution dropwise to the cetyltrimethylammonium chloride ethanol solution, heat to 78 ℃, keep it in a micro-reflux state, and continue to stir at this temperature for 6 h, then cool to 20 ℃, stand for 18 h, then filter to separate the filter cake, and then wash the filter cake with water and ethanol to remove impurities attached to the surface of the filter cake, and then dry the filter cake in a 120 ℃ air-drying oven for 8 h to obtain the catalyst.

[0058] 4. Take 1,2-pentanediol production wastewater 500 g in a 1 L beaker, add catalyst 0.5 g prepared in the above step, stir to 65 ℃, add 30% hydrogen peroxide 1.5 g under UV irradiation, continue to react for 2 h, cool, filter out the catalyst, and detect the COD of the filtrate.

[0059] The treatment effect is: the COD removal rate is 21%, the content of 1,2-pentanediol is 0.07%, and the pretreated wastewater cannot be used for subsequent microbial biochemical treatment.

[0060] As shown in Comparative Examples 1 and 2, when the catalyst of Comparative Example 1 uses conventional phosphomolybdic acid, the treatment effect is not good, and the consumption of hydrogen peroxide significantly increases, and the waste water after treatment can not be used for subsequent microbial biochemical treatment, Comparative Example 2 uses hexadecyltrimethylammonium chloride ethanol instead of benzyltriethylammonium chloride ethanol solution to prepare activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst, to the COD of waste water and 1,2-pentanediol treatment effect is not good, and the waste water after treatment can not be used for subsequent microbial biochemical treatment. The embodiment of the present invention adopts activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst to promote hydrogen peroxide oxidation reaction, and 1,2-pentanediol can be degraded at the same time, reducing the consumption of hydrogen peroxide.

Claims

1. A method for pretreating wastewater produced by the oxidation of n-pentene to produce 1,2-pentanediol, characterized by: Add activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst to the wastewater to be treated, irradiate it with ultraviolet light, and simultaneously add hydrogen peroxide to react, thereby degrading 1,2-pentanediol in the wastewater and removing COD, thereby achieving wastewater pretreatment; The activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst is prepared by dripping a peroxyphosphomolybdic acid solution into a benzyltriethylammonium chloride ethanol solution, maintaining the temperature and stirring, cooling and allowing to stand, filtering, and drying. The peroxyphosphomolybdic acid solution is obtained by dissolving phosphomolybdic acid in distilled water and reacting with hydrogen peroxide; benzyltriethylammonium chloride is added to ethanol and dissolved, and activated carbon is added to obtain the benzyltriethylammonium chloride ethanol solution.

2. The pretreatment method according to claim 1, wherein: Add activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst to the wastewater to be treated, irradiate with ultraviolet light at 60-70°C, and add hydrogen peroxide to react for 1.5-2.5 hours.

3. The pretreatment method according to claim 2, wherein: The amount of activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst used is 0.08~0.2%w / w of the mass of the wastewater to be treated, and the amount of hydrogen peroxide used is 0.25~0.4%w / w of the mass of the wastewater to be treated.

4. The pretreatment method according to claim 1, wherein: During the preparation of activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst, the amount of distilled water used was 8 to 12 times the mass of phosphomolybdic acid (w / w), and the amount of hydrogen peroxide used was 1.3 to 1.7 times the mass of phosphomolybdic acid (w / w). The amount of benzyltriethylammonium chloride used is 1.1 to 1.3 times the mass of phosphomolybdic acid w / w, the amount of ethanol used is 8 to 12 times the mass of benzyltriethylammonium chloride w / w, and the amount of activated carbon used is 3.5 to 4.5 times the mass of phosphomolybdic acid w / w.

5. The pretreatment method according to claim 1, wherein: During the preparation process of activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst, the insulation temperature is 70~78℃, the insulation stirring time is 4~8h, the temperature is lowered to 15~25℃, and the catalyst is allowed to stand for 12~24h. The drying temperature is 110~130℃ and the drying time is 7~9h.