Pretreatment method for wastewater generated in preparation of 1, 2-pentanediol by n-amylene oxidation method

Abstract

The invention belongs to the field of fine chemical engineering wastewater treatment, and particularly relates to a pretreatment method of wastewater generated in preparation of 1, 2-pentanediol by an n-amylene oxidation method. The method comprises the following steps: adding an activated carbon loaded peroxyphosphomolybdic acid quaternary ammonium salt catalyst into wastewater to be treated, performing ultraviolet irradiation, and adding hydrogen peroxide for reaction to degrade 1, 2-pentanediol in the wastewater and remove COD (Chemical Oxygen Demand), thereby realizing pretreatment of the wastewater. The activated carbon loaded peroxy phosphomolybdic acid quaternary ammonium salt catalyst can promote the oxidation reaction of hydrogen peroxide, can degrade 1, 2-pentanediol, and reduces the use amount of hydrogen peroxide.

Description

Technical Field

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

[0002] 1,2-Pentanediol is a colorless and odorless liquid and is an important intermediate for 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 many existing methods for preparing 1,2-pentanediol. According to the initial raw materials, they are divided into n-pentene method, furfural or furfuryl alcohol method, n-pentanoic acid method, n-butyraldehyde method, and n-butanol method. The n-pentene method is that the raw material reacts with hydrogen peroxide to generate epoxide, which is then hydrolyzed and ring-opened under acid or alkaline conditions to generate the final product 1,2-pentanediol. However, a large amount of wastewater will be generated in the production process of preparing 1,2-pentanediol by the n-pentene oxidation method. If this type of wastewater is not properly treated, direct discharge will cause serious pollution to the environment. Among the traditional wastewater treatment methods, biological methods are widely used because of their economy and environmental friendliness. However, when treating 1,2-pentanediol production wastewater, biological methods face huge challenges. This is mainly because 1,2-pentanediol, as the main organic component in wastewater, shows strong toxicity to microorganisms. This toxicity not only inhibits the activity of microorganisms, but also greatly reduces the efficiency of the biological treatment system. Even if the concentration of 1,2-pentanediol is reduced by diluting the wastewater, its biochemical treatment effect is still not ideal and cannot meet the relevant environmental protection standards and requirements. Therefore, direct biological treatment of 1,2-pentanediol production wastewater is obviously not a feasible solution. It is particularly important to pre-treat the wastewater before biological treatment. The purpose of pre-treatment is to reduce the concentration of 1,2-pentanediol in the wastewater or change its existence form, thereby reducing the toxic effect on microorganisms and improving the efficiency and effect of subsequent biological treatment.

[0004] Therefore, in order to solve the problem of 1,2-pentanediol production wastewater treatment, 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 preparing 1,2-pentanediol by an n-pentene oxidation process. 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 a 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-loaded peroxyphosphomolybdic acid quaternary ammonium salt 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 at a constant temperature, standing after cooling, filtering and drying; wherein, phosphomolybdic acid is dissolved in distilled water and reacted with 30% w / w hydrogen peroxide to obtain a peroxyphosphomolybdic acid solution; benzyltriethylammonium chloride is added to ethanol and dissolved, and activated carbon is added to obtain a solution.

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

[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 activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst used in the present invention 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 used.

[0019] 2. The 1,2-pentanediol of the present invention undergoes 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. The degradation products have no microbial inhibition and can be used for biochemical treatment.

[0020] 3. The activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst of the present invention 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 of the present invention reaches more than 80%, which not only solves the inhibition of 1,2-pentanediol on the activity of microorganisms, but also reduces the organic matter content of the wastewater and improves the biodegradability of the wastewater.

[0022] 5. The method of the present invention is simple to operate, low in cost, and has broad prospects for commercial application. DETAILED DESCRIPTION

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

[0024] The wastewater to be treated comes from the production process of preparing 1,2-pentanediol using n-pentene as raw material, wherein the main components of the wastewater are water and a small amount of 1,2-pentanediol entrained by azeotropy, 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 activated carbon supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst:

[0027] 1. Prepare peroxyphosphomolybdic acid solution: Take 10.0g of phosphomolybdic acid and place it in a beaker, add 100g of distilled water and stir thoroughly to ensure that the phosphomolybdic acid is completely dissolved, then add 15.0g of 30% hydrogen peroxide and stir at room temperature for 15min to obtain peroxyphosphomolybdic acid solution.

[0028] 2. Preparation of benzyltriethylammonium chloride ethanol solution: Take 12.0g of benzyltriethylammonium chloride, place it in a three-necked flask, add 120g of ethanol, stir to dissolve, and then add 40.0g of activated carbon to obtain benzyltriethylammonium chloride ethanol solution.

[0029] 3. Synthesis of catalyst: At room temperature, add peroxyphosphomolybdic acid solution dropwise into 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, and 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 peroxyphosphomolybdic acid quaternary ammonium salt 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 15min to obtain peroxyphosphomolybdic acid solution.

[0033] 2. Preparation of 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 into 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, and 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 peroxyphosphomolybdic acid quaternary ammonium salt 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, stir at room temperature for 15min, and 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 into 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, and 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 1L beaker, 0.5 g of the catalyst prepared in Example 1 was added, the temperature was raised to 65°C with stirring, 1.5 g of 30% hydrogen peroxide was added dropwise under ultraviolet irradiation, the reaction was continued for 2 h, the temperature was 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 microbial treatment to meet the treatment standards.

[0043] Example 5

[0044] 500 g of 1,2-pentanediol production wastewater was placed in a 1L beaker, 0.4 g of the catalyst prepared in Example 2 was added, the temperature was raised to 60°C with stirring, 2.0 g of 30% hydrogen peroxide was added dropwise under ultraviolet irradiation, the reaction was continued for 2.5 h, the temperature was 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 pretreated 1,2-pentanediol wastewater 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 1L beaker, 1.0 g of the catalyst prepared in Example 2 was added, the temperature was raised to 70°C with stirring, 1.25 g of 30% hydrogen peroxide was added dropwise under ultraviolet irradiation, the reaction was continued for 1.5 h, the temperature was 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 pretreated 1,2-pentanediol wastewater is suitable for microbial treatment 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 500g of 1,2-pentanediol production wastewater and place it in a 1L beaker, add 0.5g of phosphomolybdic acid catalyst, stir and heat to 65°C, add 20g of 30% hydrogen peroxide under ultraviolet irradiation, continue to react for 2h, cool down, filter out the catalyst, and detect the COD of the filtrate.

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

[0053] Comparative Example 2

[0054] The difference from Example 4 is that the preparation method of the activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst is different, and other conditions are the same as in Example 4, specifically:

[0055] 1. Prepare peroxyphosphomolybdic acid solution: Take 10.0g of phosphomolybdic acid, place it in a beaker, add 100g of distilled water and stir thoroughly to ensure that the phosphomolybdic acid is completely dissolved, then add 15.0g of 30% hydrogen peroxide, stir at room temperature for 15min, and obtain peroxyphosphomolybdic acid solution.

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

[0057] 3. Synthesis of catalyst: At room temperature, add peroxyphosphomolybdic acid solution dropwise into hexadecyltrimethylammonium 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, and dry the washed filter cake in a 120°C forced air drying oven for 8 hours to obtain the catalyst.

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

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

[0060] As can be seen from Comparative Examples 1 and 2, when the catalyst of Comparative Example 1 uses conventional phosphomolybdic acid, the treatment effect is poor, and the amount of hydrogen peroxide used is significantly increased, and the treated wastewater cannot be used for subsequent microbial biochemical treatment. When hexadecyl trimethyl ammonium chloride ethanol is used to replace benzyl triethyl ammonium chloride ethanol solution to prepare activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst, the COD and 1,2-pentanediol treatment effects of the wastewater are poor, and the treated wastewater cannot be used for subsequent microbial biochemical treatment. The embodiment of the present invention uses activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst to promote hydrogen peroxide oxidation reaction, and can degrade 1,2-pentanediol and reduce the amount of hydrogen peroxide used.

Claims

1. A method for pretreating wastewater produced by the n-pentene oxidation process for preparing 1,2-pentanediol, characterized in that: Activated carbon-loaded peroxyphosphomolybdic acid quaternary ammonium salt 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.

2. The pretreatment method according to claim 1, characterized in that: 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, characterized in that: The amount of activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst is 0.08-0.2% w / w of the mass of the wastewater to be treated, and the amount of hydrogen peroxide is 0.25-0.4% w / w of the mass of the wastewater to be treated.

4. The pretreatment method according to claim 3, characterized in that: 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 at a constant temperature, standing after cooling, filtering, and drying; wherein, phosphomolybdic acid is dissolved in distilled water and reacted with hydrogen peroxide to obtain a peroxyphosphomolybdic acid solution; benzyltriethylammonium chloride is added to ethanol and dissolved, and activated carbon is added to obtain a benzyltriethylammonium chloride ethanol solution.

5. The pretreatment method according to claim 4, characterized in that: 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; 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.

6. The pretreatment method according to claim 4, characterized in that: The insulation temperature is 70-78°C, the insulation stirring time is 4-8h, the temperature is lowered to 15-25°C, and it is allowed to stand for 12-24h. The drying temperature is 110-130°C, and the drying time is 7-9h.