Method for removing chloropropylene glycol monomethyl ether in epichlorohydrin wastewater

Abstract

The invention relates to a method for removing chloropropylene glycol monomethyl ether in epichlorohydrin wastewater, which comprises the following steps: in a hydrogen atmosphere, contacting the epichlorohydrin wastewater with a hydrodechlorination catalyst to carry out hydrodechlorination reaction, so that the chloropropylene glycol monomethyl ether in the epichlorohydrin wastewater is converted into propylene glycol monomethyl ether, wherein the hydrodechlorination catalyst comprises an activated carbon carrier and an active metal component; the active metal component comprises Ru. According to the method, the chloropropylene glycol monomethyl ether in the epichlorohydrin wastewater can be efficiently removed, the propylene glycol monomethyl ether product with higher value is obtained, and the treatment cost of the chloropropylene glycol monomethyl ether is reduced.

Description

A method for removing chloropropanediol monomethyl ether from epichlorohydrin wastewater Technical Field

[0001] This application relates to the field of catalytic chemistry technology, and more specifically, to a method for removing chloropropane glycol monomethyl ether from epichlorohydrin wastewater. Background Technology

[0002] Epichlorohydrin is a widely used basic organic chemical raw material, a major component in the synthesis of epoxy resins, chlorohydrin rubbers, pesticides, and surfactants. Currently, epichlorohydrin is mainly produced through the chlorohydrin process and the glycerol process, but these methods generate significant amounts of waste. To address these issues, researchers have begun using hydrogen peroxide, a green oxidant, coupled with titanium silicate molecular sieves as a catalyst, to directly epoxidize 3-chloropropene to epichlorohydrin in a mixed solution of methanol and water. This represents a new generation of green and environmentally friendly epichlorohydrin production technology.

[0003] CN101747296A and CN101747297A disclose a method for producing epichlorohydrin from the epoxidation reaction of 3-chloropropene and hydrogen peroxide. This method achieves continuous and stable synthesis of epichlorohydrin with a hydrogen peroxide conversion rate of not less than 97% and a selectivity of not less than 95%. However, the selectivity of epichlorohydrin is currently not 100%, primarily because epichlorohydrin undergoes a ring-opening side reaction with methanol after formation, yielding the byproduct 1-chloro-3-methoxy-2-propanol (abbreviated as chloropropanediol monomethyl ether). Chlorinated organic compounds are a class of surface water and soil pollutants, exhibiting significant toxicity and carcinogenicity to humans and animals. Therefore, the toxic and harmful chloropropanediol monomethyl ether needs to be treated. Furthermore, chloropropanediol monomethyl ether has low added value and high treatment costs, increasing the overall cost of the hydrogen peroxide-based epichlorohydrin production process. Therefore, it is necessary to further reduce the treatment cost of chloropropanediol monomethyl ether and improve the technical and economic efficiency of the entire reaction process. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for removing chloropropane glycol monomethyl ether from epichlorohydrin wastewater, which can efficiently remove chloropropane glycol monomethyl ether from epichlorohydrin wastewater and obtain a higher-value propylene glycol monomethyl ether product, thereby reducing the treatment cost of chloropropane glycol monomethyl ether.

[0005] To achieve the above objectives, this disclosure provides a method for removing chloropropane glycol monomethyl ether from epichlorohydrin wastewater, comprising the following steps: in a hydrogen atmosphere, contacting epichlorohydrin wastewater with a hydrodechlorination catalyst to perform a hydrodechlorination reaction, thereby converting the chloropropane glycol monomethyl ether in the epichlorohydrin wastewater into propylene glycol monomethyl ether; wherein the hydrodechlorination catalyst comprises an activated carbon support and an active metal component; the active metal component comprises Ru.

[0006] Optionally, based on the total weight of the hydrodechlorination catalyst, the content of the active metal component is 0.1 to 14% by weight, preferably 1 to 12% by weight.

[0007] Optionally, the total specific surface area of ​​the hydrodechlorination catalyst is 1000~2000 m². 2 / g, preferably 1700~2000m 2 / g; particle size is 10~200 mesh, preferably 30~100 mesh.

[0008] Optionally, the microporous specific surface area of ​​the hydrodechlorination catalyst accounts for 70-90% of the total specific surface area.

[0009] Optionally, the hydrodechlorination catalyst is prepared by a method including the following steps: (1) impregnating and drying an activated carbon support with an active metal precursor solution to obtain a catalyst precursor; optionally, the active metal precursor includes RuCl3; (2) calcining and reducing the catalyst precursor under hydrogen conditions.

[0010] Optionally, in step (1), the Ru in the active metal precursor solution 3+ The concentration is 0.04~6.0% by weight, preferably 0.4~5.0% by weight; preferably, the impregnation treatment is equal-volume impregnation; the impregnation temperature is 20~30℃, and the impregnation time is 10~15h; optionally, the drying treatment conditions include: drying temperature of 100~120℃, and drying time of 6~10h; optionally, in step (2), the calcination reduction treatment conditions include: reduction temperature of 300~800℃, preferably 300~600℃; reduction time of 2~8h, preferably 3~6h; hydrogen flow rate of 5~100 mL / min, preferably 5~50 mL / min.

[0011] Optionally, the epichlorohydrin wastewater is derived from the reaction of 3-chloropropene and hydrogen peroxide epoxidation to synthesize epichlorohydrin; optionally, based on the total weight of the epichlorohydrin wastewater, the content of chloropropanediol monomethyl ether is 0.1~10% by weight, preferably 0.7~7% by weight.

[0012] Optionally, the epichlorohydrin wastewater further includes methanol and water; based on the total weight of the epichlorohydrin wastewater, the methanol content is 20-80% by weight, preferably 40-60% by weight.

[0013] Optionally, in the hydrodechlorination reaction, the weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst is 100:0.1~8, preferably 100:0.1~4.

[0014] Optionally, the conditions for the hydrodechlorination reaction include: a reaction temperature of 140~220℃, a reaction time of 1~10h, and a hydrogen pressure of 5~100bar.

[0015] Optionally, the conditions for the hydrodechlorination reaction include: a reaction temperature of 160~200℃, a reaction time of 1~6h, and a hydrogen pressure of 5~50bar.

[0016] This disclosure provides a method for removing chloropropane glycol monomethyl ether from epichlorohydrin wastewater. The hydrodechlorination catalyst used in this disclosure has metal Ru as the active center and activated carbon as the support, exhibiting excellent catalytic activity for the hydrodechlorination reaction of chloropropane glycol monomethyl ether. This disclosure involves hydrodechlorinating epichlorohydrin wastewater in a hydrogen atmosphere using the catalytic action of the hydrodechlorination catalyst, converting the low-value-added chloropropane glycol monomethyl ether into the high-value-added 1-methoxy-2-propanol (hereinafter referred to as propylene glycol monomethyl ether). Propylene glycol monomethyl ether is a colorless and transparent liquid with low volatility and toxicity. It is mainly used as a solvent in organic synthesis and can be used to synthesize aliphatic polyethers, resins, and other chemicals. It is also used in the preparation of coatings, inks, cleaning agents, camphor, and other products. Industrially, it also has applications as a cleaning agent, adhesive remover, and refrigerant. This disclosure allows for the simultaneous processing of chloropropanediol monomethyl ether (PPD) to obtain a higher-value PPD product, thereby reducing the processing cost of PPD and improving the techno-economic efficiency of the hydroperoxide-based epichlorohydrin production process.

[0017] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0018] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0019] This disclosure provides a method for removing chloropropane glycol monomethyl ether from epichlorohydrin wastewater, comprising the following steps: in a hydrogen atmosphere, contacting epichlorohydrin wastewater with a hydrodechlorination catalyst to perform a hydrodechlorination reaction, thereby converting the chloropropane glycol monomethyl ether in the epichlorohydrin wastewater into propylene glycol monomethyl ether; wherein the hydrodechlorination catalyst comprises an activated carbon support and an active metal component; the active metal component comprises Ru.

[0020] This disclosure provides a method for removing chloropropane glycol monomethyl ether from epichlorohydrin wastewater. The hydrodechlorination catalyst used in this disclosure has metal Ru as the active center and activated carbon as the support, exhibiting excellent catalytic activity for the hydrodechlorination reaction of chloropropane glycol monomethyl ether. This disclosure involves hydrodechlorinating epichlorohydrin wastewater in a hydrogen atmosphere using the catalytic action of the hydrodechlorination catalyst, converting the low-value-added chloropropane glycol monomethyl ether into the high-value-added 1-methoxy-2-propanol (hereinafter referred to as propylene glycol monomethyl ether). Propylene glycol monomethyl ether is a colorless and transparent liquid with low volatility and toxicity. It is mainly used as a solvent in organic synthesis and can be used to synthesize aliphatic polyethers, resins, and other chemicals. It is also used in the preparation of coatings, inks, cleaning agents, camphor, and other products. Industrially, it also has applications as a cleaning agent, adhesive remover, and refrigerant. This disclosure allows for the simultaneous processing of chloropropanediol monomethyl ether (PPD) to obtain a higher-value PPD product, thereby reducing the processing cost of PPD and improving the techno-economic efficiency of the hydroperoxide-based epichlorohydrin production process.

[0021] In one embodiment, the content of the active metal component is 0.1 to 14% by weight, based on the total weight of the hydrodechlorination catalyst. When the loading of the active metal component is within the range of this embodiment, the catalyst can exhibit higher catalytic activity in the hydrodechlorination reaction of chloropropanediol monomethyl ether.

[0022] In a preferred embodiment, the content of the active metal component is 1-12% by weight, based on the total weight of the hydrodechlorination catalyst. When the content of the active metal component Ru in the hydrodechlorination catalyst is within the preferred range, the conversion rate of chloropropanediol monomethyl ether and the selectivity of propylene glycol monomethyl ether can be further improved.

[0023] In one specific embodiment, the total specific surface area of ​​the hydrodechlorination catalyst is 1000~2000 m². 2 / g, preferably 1700~2000 m 2 / g; the particle size is 10~200 mesh, preferably 30~100 mesh, and more preferably 30~60 mesh. The catalyst provided in this disclosure has a suitable specific surface area and particle size. The catalyst can be in the form of unground particles. The size of the catalyst particles has a certain influence on the catalytic activity. The larger the size, the lower the mass transfer effect and the lower the activity, requiring a higher catalyst addition amount. However, the catalyst mesh size should not be further reduced, otherwise even if an extremely excessive amount of catalyst is added, the desired effect may not be achieved. Therefore, the catalyst used in this disclosure has a particle size range that balances the addition amount and catalytic activity, and is more suitable for use in fixed-bed reactors.

[0024] In a preferred embodiment, the microporous specific surface area of ​​the hydrodechlorination catalyst accounts for 70-90% of the total specific surface area, preferably 70-80%. When the proportion of the catalyst's microporous specific surface area is within this range, it is more adaptable to the hydrodechlorination reaction of macromolecular reaction substrates (chloropropanediol monomethyl ether), resulting in better mass transfer. In this disclosure, micropores refer to pores with a diameter of less than 2 nm.

[0025] In one specific embodiment, the hydrodechlorination catalyst is prepared by a method including the following steps: (1) impregnating and drying an activated carbon support with an active metal precursor solution to obtain a catalyst precursor; optionally, the active metal precursor includes RuCl3; (2) calcining and reducing the catalyst precursor under hydrogen conditions.

[0026] In one specific embodiment, in step (1), the Ru in the active metal precursor solution... 3+ The concentration is 0.04~6.0% by weight, preferably 0.4~5.0% by weight; preferably, the impregnation treatment is equal volume impregnation, which can be carried out by conventional operation; wherein the impregnation temperature can be 20~30℃, and the impregnation time can be 10~15h; optionally, the drying conditions include: drying temperature of 100~120℃, and drying time of 6~10h.

[0027] In a preferred embodiment, the conditions for the calcination reduction treatment in step (2) include: a reduction temperature of 300~800℃, preferably 300~600℃; a reduction time of 2~8h, preferably 3~6h; and a hydrogen flow rate of 5~100 mL / min, preferably 5~50 mL / min. According to the process conditions in this embodiment, especially the preferred process conditions, a catalyst with higher catalytic activity can be prepared.

[0028] In one specific embodiment, the epichlorohydrin wastewater originates from the reaction of 3-chloropropene with hydrogen peroxide to synthesize epichlorohydrin; specifically, the epichlorohydrin wastewater originates from the liquid after separating the unreacted substrate 3-chloropropene and the target product epichlorohydrin from the reaction solution; optionally, based on the total weight of the epichlorohydrin wastewater, the content of chloropropanediol monomethyl ether is 0.1~10% by weight, preferably 0.7~7% by weight. The method provided in this embodiment effectively removes chloropropanediol monomethyl ether from epichlorohydrin wastewater within a wide range of concentrations, and has a wide range of applications.

[0029] In one specific embodiment, the epichlorohydrin wastewater further includes methanol and water; based on the total weight of the epichlorohydrin wastewater, the methanol content is 20-80% by weight, preferably 40-60% by weight.

[0030] In one embodiment, in the hydrodechlorination reaction, the weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst is 100:0.1~8, preferably 100:0.1~4. The weight ratio of oxidation wastewater to hydrodechlorination catalyst provided in this embodiment, especially within the preferred range, is beneficial for improving the catalytic reaction effect.

[0031] In one embodiment, the conditions for the hydrodechlorination reaction include: a reaction temperature of 140-220°C, a reaction time of 1-10 hours, and a hydrogen pressure of 5-100 bar. The hydrodechlorination reaction conditions provided in this embodiment can effectively remove chloropropane glycol monomethyl ether from epichlorohydrin wastewater.

[0032] In a preferred embodiment, the hydrodechlorination reaction conditions include: a reaction temperature of 160-200°C, a reaction time of 1-6 hours, and a hydrogen pressure of 5-50 bar. The preferred hydrodechlorination reaction conditions provided by this embodiment can further improve the removal efficiency of chloropropane glycol monomethyl ether from epichlorohydrin wastewater.

[0033] According to this disclosure, the hydrogenation and dechlorination reaction of chloropropanediol monomethyl ether is carried out by stirring, and the required reactor can be a stainless steel reactor with a polytetrafluoroethylene liner, a Hastelloy reactor, or a reactor conventionally used in the art.

[0034] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0035] The content of active metal components in the catalyst was obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES); the total specific surface area and microporous specific surface area of ​​the catalyst were obtained by static capacity adsorption analysis.

[0036] The particle size of the catalyst is controlled by the mesh size of the sieve used for sieving.

[0037] After the hydrodechlorination reaction of chloropropanediol monomethyl ether is completed, the concentrations of chloropropanediol monomethyl ether and propylene glycol monomethyl ether in the epichlorohydrin wastewater before and after the reaction can be analyzed by gas chromatography (Agilent 6890N), thereby calculating the conversion rate of chloropropanediol monomethyl ether and the selectivity of propylene glycol monomethyl ether.

[0038] Wherein, the conversion rate of chloropropanediol monomethyl ether (%) = (initial concentration of chloropropanediol monomethyl ether - concentration of chloropropanediol monomethyl ether after reaction) / initial concentration of chloropropanediol monomethyl ether × 100%; the selectivity of propylene glycol monomethyl ether (%) = molar concentration of propylene glycol monomethyl ether / (initial molar concentration of chloropropanediol monomethyl ether - molar concentration of chloropropanediol monomethyl ether after reaction) × 100%.

[0039] Preparation Example 1 This preparation example is used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C1), an activated carbon support, and an active metal component; the active metal component includes Ru, and the content of the active metal component Ru is 1% by weight based on the total weight of the hydrodechlorination catalyst. Specifically, the preparation includes the following steps: First, the equivalent water absorption of 1 gram of activated carbon is measured to be 2.5 grams; then, 2.52 grams of RuCl3 aqueous solution (active metal precursor solution, Ru...) is added... 3+ A catalyst precursor was prepared by impregnation of 0.4% by weight and 1 gram of activated carbon (30 mesh) in equal amounts. The impregnation temperature was 25℃ and the impregnation time was 12h. The catalyst precursor was dried and then calcined and reduced in a hydrogen atmosphere to obtain the catalyst. The drying temperature was 110℃ and the drying time was 8h. The calcination and reduction temperature was 550℃ and the calcination and reduction time was 3h. The hydrogen flow rate was 35 mL / min.

[0040] The total specific surface area of ​​the obtained catalyst C1 is 1765 m². 2 / g, of which the microporous specific surface area accounts for 73.2%.

[0041] Preparation Comparative Example 1 This comparative example was used to prepare a hydrodechlorination catalyst (Pd / C catalyst, denoted as D1), an activated carbon support, and an active metal component; the active metal component included Pd, and the content of Pd in ​​the active metal component was 1% by weight, based on the total weight of the hydrodechlorination catalyst. This comparative example followed the method in Preparation Example 1, except that the active metal precursor solution was replaced with 2.52 g of PdCl2 precursor solution. 2+ The concentration is 0.4% by weight.

[0042] Preparation Comparative Example 2: This comparative example was used to prepare a hydrodechlorination catalyst (Pt / C catalyst, denoted as D2), an activated carbon support, and an active metal component; the active metal component included Pt, and the content of Pt was 1% by weight based on the total weight of the hydrodechlorination catalyst; this comparative example followed the method in Preparation Example 1, except that the active metal precursor solution was replaced with 2.52 g of H2PtCl6 precursor solution, and Pt... 4+ The concentration is 0.4% by weight.

[0043] Preparation Example 2: This preparation example was used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C2), an activated carbon support, and an active metal component; the active metal component included Ru, and the content of the active metal component Ru was 2% by weight based on the total weight of the hydrodechlorination catalyst; this preparation example followed the method in Preparation Example 1, except that 2.54 g of RuCl3 precursor solution was used, and Ru... 3+The concentration was 0.8% by weight, and the rest of the process was the same as in Preparation Example 1.

[0044] Preparation Example 3: This preparation example was used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C3), an activated carbon support, and an active metal component; the active metal component included Ru, and the content of the active metal component Ru was 6% by weight based on the total weight of the hydrodechlorination catalyst; this preparation example followed the method in Preparation Example 1, except that 2.63 g of RuCl3 precursor solution was used, and Ru... 3+ The concentration was 2.4% by weight, and the rest of the process was the same as in Preparation Example 1.

[0045] Preparation Example 4: This preparation example was used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C4), an activated carbon support, and an active metal component; the active metal component included Ru, and the content of Ru was 12% by weight based on the total weight of the hydrodechlorination catalyst; this preparation example followed the method in Preparation Example 1, except that 2.78 g of RuCl3 precursor solution was used, and Ru... 3+ The concentration was 4.9% by weight, and the rest of the process was the same as in Preparation Example 1.

[0046] Preparation Example 5: This preparation example was used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C5), an activated carbon support, and an active metal component; the active metal component included Ru, and the content of the active metal component Ru was 0.2% by weight based on the total weight of the hydrodechlorination catalyst; this preparation example followed the method in Preparation Example 1, except that 2.50 g of RuCl3 precursor solution was used, and Ru... 3+ The concentration was 0.08% by weight, and the rest of the process was the same as in Preparation Example 1.

[0047] Preparation Example 6: This preparation example was used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C6), an activated carbon support, and an active metal component; the active metal component included Ru, and the content of the active metal component Ru was 14% by weight based on the total weight of the hydrodechlorination catalyst; this preparation example followed the method in Preparation Example 1, except that 2.83 g of RuCl3 precursor solution was used, and Ru... 3+ The concentration was 5.74% by weight, and the rest of the process was the same as in Preparation Example 1.

[0048] Preparation Example 7: This preparation example was used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C7). This preparation example follows the method described in Preparation Example 1, except that the calcination reduction temperature was 800°C, the calcination reduction time was 2 h, and the hydrogen flow rate was 100 mL / min. The remaining processes were the same as in Preparation Example 1, resulting in the hydrodechlorination catalyst C7. Catalyst C7 comprises an activated carbon support and an active metal component. The active metal component includes Ru, and the content of the active metal component Ru is 1% by weight based on the total weight of the hydrodechlorination catalyst.

[0049] Preparation Example 8: This preparation example was used to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C8). This preparation example follows the method described in Preparation Example 1, except that the activated carbon support was replaced. The specific surface area of ​​the replaced activated carbon support was 1627 m². 2 / g, the microporous specific surface area ratio is 95.0%; the rest of the process is the same as in Preparation Example 1, and the hydrogenation catalyst C8 is prepared.

[0050] The active metal content and structural characteristic parameters of the catalysts obtained in the above preparation examples are listed in Table 1 below.

[0051] Table 1

[0052] In the above preparation examples and comparative examples, the catalysts were all sieved using a 30-mesh sieve.

[0053] The following examples illustrate the catalytic effect of the catalyst obtained in the above preparation examples in the reaction of removing chloropropane glycol monomethyl ether from epichlorohydrin wastewater.

[0054] In Example 1, 50 g of epoxidized wastewater containing 50% methanol and 0.601 wt% chloropropane glycol monomethyl ether was added to a 100 mL Hastelloy reactor. 0.4 g of the Ru / C hydrodechlorination catalyst C1 (Ru content 1 wt%) from Example 1 was added, with a weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst of 100:0.8. The hydrodechlorination reaction was carried out under a hydrogen atmosphere under the following conditions: hydrogen pressure of 10 bar, reaction temperature of 160 °C, reaction time of 1 h, and rotation speed of 500 r / min. After the reaction, the catalyst was filtered, and the resulting reaction solution was analyzed by gas chromatography. The conversion rate and selectivity of chloropropane glycol monomethyl ether were calculated, and the test results are listed in Table 2.

[0055] Comparative Examples 1 and 2 follow the method described in Example 1, except that the catalysts are replaced with catalyst D1 (Pd / C) obtained in Comparative Example 1 and catalyst D2 (Pt / C) obtained in Comparative Example 2, respectively.

[0056] Example 2 This example refers to the method in Example 1, except that the reaction temperature is increased to 180°C. The rest of the process is the same as in Example 1. The test results are listed in Table 2.

[0057] Example 3 This example refers to the method in Example 1, except that the reaction temperature is increased to 200°C. The rest of the process is the same as in Example 1. The test results are listed in Table 2.

[0058] Example 4 This example refers to the method in Example 2, except that the Ru / C hydrodechlorination catalyst C2 (Ru content is 2% by weight) in Example 2 is used. The rest of the process is the same as in Example 2. The test results are listed in Table 2.

[0059] Example 5 This example follows the method in Example 2, except that the Ru / C hydrodechlorination catalyst C3 (Ru content is 6% by weight) from Example 3 is used. The rest of the process is the same as in Example 2. The test results are listed in Table 2.

[0060] Example 6 This example follows the method in Example 2, except that the Ru / C hydrodechlorination catalyst C4 (Ru content is 10% by weight) from Example 4 is used. The rest of the process is the same as in Example 2. The test results are listed in Table 2.

[0061] Example 7 This example refers to the method in Example 6, except that the concentration of chloropropane glycol monomethyl ether in epichlorohydrin wastewater is increased to 1.860% by weight. The rest of the process is the same as in Example 6. The test results are listed in Table 2.

[0062] Example 8 This example refers to the method in Example 6, except that the concentration of chloropropane glycol monomethyl ether in epichlorohydrin wastewater is increased to 3.765% by weight. The rest of the process is the same as in Example 6. The test results are listed in Table 2.

[0063] Example 9 This example refers to the method in Example 6, except that the concentration of chloropropane glycol monomethyl ether in epichlorohydrin wastewater is increased to 6.236% by weight. The rest of the process is the same as in Example 6. The test results are listed in Table 2.

[0064] Example 10 This example refers to the method in Example 9, except that the reaction time is extended to 2 hours. The rest of the process is the same as in Example 9. The test results are listed in Table 2.

[0065] Example 11 This example refers to the method in Example 9, except that the reaction time is extended to 4 hours. The rest of the process is the same as in Example 9. The test results are listed in Table 2.

[0066] Example 12 This example refers to the method in Example 9, except that the reaction time is extended to 6 hours. The rest of the process is the same as in Example 9. The test results are listed in Table 2.

[0067] Example 13 This example follows the method in Example 1, except that the catalyst is replaced with catalyst C5 (Ru content is 0.2% by weight) obtained in Preparation Example 5.

[0068] Example 14 This example follows the method in Example 1, except that the catalyst is replaced with the catalyst C6 (Ru content is 14% by weight) obtained in Preparation Example 6.

[0069] Example 15 This example follows the method in Example 1, except that the catalyst is replaced with the catalyst C7 obtained in Preparation Example 7.

[0070] Example 16 This example refers to the catalytic reaction method in Example 1, except that 4g of catalyst C1 is added to 50g of epichlorohydrin wastewater, and the weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst is 100:8. The rest of the process is the same as in Example 1.

[0071] Example 17 The catalytic reaction method in Example 1 is the same as that in Example 1, except that the reaction temperature is 140°C, the reaction time is 10h, the hydrogen pressure is 60bar, and the rest of the process is the same as in Example 1. The test results are listed in Table 2.

[0072] Example 18 The catalytic reaction method in Example 1 is the same as in Example 1, except that the catalyst is replaced with the catalyst C8 obtained in Preparation Example 8. The rest of the process is the same as in Example 1. The test results are listed in Table 2.

[0073] The conversion rates and selectivity of propylene glycol monomethyl ether obtained from the above examples and comparative examples are listed in Table 2 below.

[0074] Table 2

[0075] Comparing the results of Example 1 and Comparative Examples 1-2, it can be seen that after changing the active center, no target product propylene glycol monomethyl ether was generated, indicating that Ru is the active center for the hydrodechlorination of chloropropanediol monomethyl ether. Only by using the hydrodechlorination catalyst provided in this disclosure can the hydrodechlorination of chloropropanediol monomethyl ether be converted into propylene glycol monomethyl ether.

[0076] A comparison of the results from Examples 1-3 shows that increasing the reaction temperature can improve the conversion rate of chloropropanediol monomethyl ether, but the selectivity of the target product, propylene glycol monomethyl ether, decreases. In Example 17, decreasing the reaction temperature significantly reduces the catalyst activity; even with a significantly extended reaction time, the conversion rate of chloropropanediol monomethyl ether and the selectivity of the target product, propylene glycol monomethyl ether, remain low. A comparison of Examples 1-3 with Example 17 shows that when the reaction is carried out according to the preferred hydrodechlorination conditions provided in this disclosure, superior catalytic performance can be obtained.

[0077] Comparing the results of Examples 2 and 4-6, it can be seen that increasing the active center loading can slowly increase the conversion rate of chloropropanediol monomethyl ether and significantly improve the selectivity of propylene glycol monomethyl ether. Comparing the results of Examples 1 and 13-14, it can be seen that when the active center loading in catalyst C5 used in Example 13 is too low, both the conversion rate of chloropropanediol monomethyl ether and the selectivity of the target product propylene glycol monomethyl ether are low, indicating low reaction activity. When the loading in catalyst C6 used in Example 14 is too high, although it can significantly improve the conversion rate of chloropropanediol monomethyl ether and the selectivity of the target product propylene glycol monomethyl ether, thus improving catalytic activity, the excessive loading leads to increased catalyst cost and a darker solution color after the reaction, indicating significant loss of active centers. Therefore, it is shown that the active metal loading of the catalysts used in Examples 1-2 and 4-6, within the preferred range provided in this disclosure, can achieve higher catalytic activity and better economic efficiency.

[0078] Comparing the results of Examples 6 and 7-9, it can be seen that by increasing the concentration of the reactant chloropropanediol monomethyl ether, its conversion rate gradually decreases, and the selectivity of propylene glycol monomethyl ether slowly decreases. When the content of chloropropanediol monomethyl ether in epichlorohydrin wastewater is within the preferred range provided in this disclosure, a higher conversion rate and selectivity of chloropropanediol monomethyl ether can be achieved.

[0079] Comparing the results of Examples 9 and 10-12, it can be seen that by increasing the reaction time, the conversion rate of chloropropanediol monomethyl ether increases significantly. The catalytic reaction carried out in Examples 9-12 according to the preferred reaction time provided in this disclosure can achieve better catalytic reaction effect.

[0080] Comparing the results of Example 1 and Example 15, it can be seen that the calcination and reduction conditions of catalyst C7 used in Example 15 are not within the preferred range of this disclosure, and increasing the calcination and reduction temperature of the catalyst leads to a decrease in catalyst activity. The catalyst C1 used in Example 1, prepared according to the preferred conditions provided in this disclosure, has better catalytic activity.

[0081] Comparing the results of Examples 1 and 16, it can be seen that increasing the amount of catalyst used can improve the conversion rate of chloropropanediol monomethyl ether and the selectivity of the target product propylene glycol monomethyl ether. However, in Example 16, excessive use of catalyst not only increases the cost of catalyst use but also affects the external diffusion mass transfer effect. In Example 1, the hydrodechlorination reaction was carried out according to the preferred catalyst addition amount of this disclosure, resulting in better performance per unit mass of catalyst.

[0082] Comparing the results of Example 1 and Example 18, it can be seen that, while keeping the total specific surface area of ​​the catalyst essentially unchanged, increasing the proportion of micropore specific surface area in the catalyst leads to a decrease in catalyst activity. This indicates that the substrate, chloropropanediol monomethyl ether, has a relatively large molecule, and excessive micropores are detrimental to its mass transfer. The micropore specific surface area ratio of catalyst C1 used in Example 1, within the optimized range provided in this disclosure, can achieve better reaction results.

[0083] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0084] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0085] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for removing chloropropanediol monomethyl ether from epichlorohydrin wastewater, characterized in that, Includes the following steps: In a hydrogen atmosphere, epichlorohydrin wastewater is contacted with a hydrodechlorination catalyst to carry out a hydrodechlorination reaction, thereby converting chloropropane glycol monomethyl ether in the epichlorohydrin wastewater into propylene glycol monomethyl ether; wherein the hydrodechlorination catalyst comprises an activated carbon support and an active metal component; the active metal component comprises Ru.

2. The method according to claim 1, characterized in that, Based on the total weight of the hydrodechlorination catalyst, the content of the active metal component is 0.1-14% by weight, preferably 1-12% by weight.

3. The method according to claim 1, characterized in that, The total specific surface area of ​​the hydrodechlorination catalyst is 1000~2000 m². 2 / g, preferably 1700~2000 m 2 / g; particle size is 10~200 mesh, preferably 30~100 mesh.

4. The method according to claim 3, characterized in that, The microporous specific surface area of ​​the hydrodechlorination catalyst accounts for 70-90% of the total specific surface area.

5. The method according to claim 1, characterized in that, The hydrodechlorination catalyst is prepared by a method including the following steps: (1) impregnating and drying an activated carbon support with an active metal precursor solution to obtain a catalyst precursor; Optionally, the active metal precursor includes RuCl3; (2) The catalyst precursor is calcined and reduced under hydrogen conditions.

6. The method according to claim 5, characterized in that, In step (1), Ru in the active metal precursor solution 3 + The concentration is 0.04~6.0% by weight, preferably 0.4~5.0% by weight; preferably, the impregnation treatment is equal volume impregnation; The impregnation temperature is 20~30℃ and the impregnation time is 10~15h; optionally, the drying conditions include: drying temperature of 100~120℃ and drying time of 6~10h; optionally, in step (2), the calcination reduction conditions include: reduction temperature of 300~800℃, preferably 300~600℃; reduction time of 2~8h, preferably 3~6h; hydrogen flow rate of 5~100 mL / min, preferably 5~50 mL / min.

7. The method according to claim 1, characterized in that, The epichlorohydrin wastewater is derived from the reaction of 3-chloropropene and hydrogen peroxide epoxidation to synthesize epichlorohydrin; optionally, based on the total weight of the epichlorohydrin wastewater, the content of chloropropanediol monomethyl ether is 0.1~10% by weight, preferably 0.7~7% by weight.

8. The method according to claim 6, characterized in that, The epichlorohydrin wastewater also includes methanol and water; based on the total weight of the epichlorohydrin wastewater, the methanol content is 20-80% by weight, preferably 40-60% by weight.

9. The method according to claim 1, characterized in that, In the hydrodechlorination reaction, the weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst is 100:0.1~8, preferably 100:0.1~4.

10. The method according to claim 1, characterized in that, The conditions for the hydrodechlorination reaction include: a reaction temperature of 140~220℃, a reaction time of 1~10h, and a hydrogen pressure of 5~100bar.

11. The method according to claim 9, characterized in that, The conditions for the hydrodechlorination reaction include: a reaction temperature of 160~200℃, a reaction time of 1~6h, and a hydrogen pressure of 5~50bar.

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