Method for removing chloropropylene glycol in epichlorohydrin wastewater

Abstract

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

Description

Technical Field

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

[0002] Hydrogen peroxide is a green oxidant, and its catalytic oxidation system with titanium silicate molecular sieves can yield a variety of oxidation or epoxidation products. For example, in a mixed solution of methanol and water, using titanium silicate molecular sieves as a catalyst, 3-chloropropene can be directly epoxidized to epichlorohydrin, which is currently a new generation of green epichlorohydrin production technology. The resulting epichlorohydrin is a widely used basic organic chemical raw material, and is a major raw material for the synthesis of epoxy resins, chlorohydrin rubbers, pesticides, surfactants, and other products.

[0003] Several institutions have reported technologies for preparing epichlorohydrin using the hydrogen peroxide method. For example, CN101747296A and CN101747297A disclose methods for producing epichlorohydrin through the epoxidation reaction of 3-chloropropene and hydrogen peroxide. These methods achieve 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%. A major reason why the selectivity of epichlorohydrin does not currently reach 100% is that epichlorohydrin undergoes a ring-opening side reaction with water after formation, yielding the byproduct 3-chloro-1,2-propanediol (chloropropanediol for short). Furthermore, chloropropanediol has low added value and high wastewater treatment costs, increasing the overall cost of the hydrogen peroxide method for epichlorohydrin production. Therefore, it is necessary to reduce the treatment cost of chloropropanediol and improve the techno-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 from epichlorohydrin wastewater, which can efficiently remove chloropropane glycol from epichlorohydrin wastewater and obtain a higher-value propylene glycol product, thereby reducing the treatment cost of chloropropane glycol.

[0005] To achieve the above objectives, this disclosure provides a method for removing chloropropane glycol from epichlorohydrin wastewater, comprising the following steps: In a hydrogen atmosphere, epichlorohydrin wastewater is contacted with a hydrodechlorination catalyst to carry out a catalytic hydrodechlorination reaction, thereby converting chloropropane glycol in the epichlorohydrin wastewater into propylene glycol; 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 15% by weight, preferably 0.7 to 10% by weight.

[0007] Optionally, the BET specific surface area of ​​the hydrodechlorination catalyst is 1000~2000 m². 2 / g, preferably 1500~2000 m 2 / g; particle size is 10~200 mesh, preferably 30~120 mesh.

[0008] Optionally, the hydrodechlorination catalyst is prepared by a method comprising the following steps: (1) The activated carbon support is impregnated with an active metal precursor solution and then dried to obtain a catalyst precursor; optionally, the active metal precursor includes RuCl3; (2) The catalyst precursor is calcined and reduced under hydrogen conditions.

[0009] Optionally, in step (1), the Ru in the active metal precursor solution 3+ The concentration is 0.05~7.5% by weight, preferably 0.35~5.0% by weight. Preferably, the impregnation treatment is an equal-volume impregnation; the impregnation temperature is 20~30℃, and the impregnation time is 10~15h; Optionally, the drying conditions include: a drying temperature of 100~120℃ and a drying time of 6~10h; Optionally, in step (2), the conditions for the calcination reduction treatment 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.

[0010] Optionally, the epichlorohydrin wastewater originates from the reaction of 3-chloropropene with hydrogen peroxide to synthesize epichlorohydrin; Optionally, based on the total weight of the epichlorohydrin wastewater, the content of chloropropanediol is 0.1 to 4% by weight, preferably 0.1 to 1.8% by weight.

[0011] 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.

[0012] Optionally, in the catalytic hydrodechlorination reaction, the weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst is 100:0.1~8, preferably 100:0.1~4.

[0013] Optionally, the conditions for the catalytic hydrodechlorination reaction include: a reaction temperature of 120~220℃, a reaction time of 1~10h, and a hydrogen pressure of 5~100bar.

[0014] Optionally, the conditions for the catalytic hydrodechlorination reaction include: a reaction temperature of 160~200℃, a reaction time of 1~5h, and a hydrogen pressure of 5~60bar.

[0015] This disclosure provides a method for removing chloropropane glycol from epichlorohydrin wastewater. The hydrodechlorination catalyst used in this disclosure has metallic Ru as the active center and activated carbon as the support, exhibiting excellent catalytic activity for the hydrodechlorination reaction of chloropropane glycol. This disclosure involves hydrodechlorinating epichlorohydrin wastewater in a hydrogen atmosphere using the catalytic action of the hydrodechlorination catalyst, converting low-value-added chloropropane glycol into high-value-added 1,2-propanediol (hereinafter referred to as propylene glycol). Propylene glycol is an important raw material for unsaturated polyesters, epoxy resins, polyurethane resins, plasticizers, and surfactants, and has wide applications in the chemical, food, and pharmaceutical industries. The method provided in this disclosure can obtain the higher-value propylene glycol product while treating chloropropane glycol, reducing the treatment cost of chloropropane glycol and thus improving the techno-economic efficiency of the hydrogen peroxide-based epichlorohydrin production process.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0017] 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.

[0018] This disclosure provides a method for removing chloropropane glycol from epichlorohydrin wastewater, comprising the following steps: In a hydrogen atmosphere, epichlorohydrin wastewater is contacted with a hydrodechlorination catalyst to carry out a catalytic hydrodechlorination reaction, converting chloropropane glycol in the epichlorohydrin wastewater into propylene glycol. The hydrodechlorination catalyst comprises an activated carbon support and an active metal component, the active metal component of which is Ru. This disclosure provides a method for removing chloropropane glycol from epichlorohydrin wastewater. The hydrodechlorination catalyst used has Ru as the active center and activated carbon as the support, exhibiting excellent catalytic activity for the hydrodechlorination reaction of chloropropane glycol. This disclosure utilizes the catalytic action of a hydrodechlorination catalyst to hydrodechlorinate epichlorohydrin wastewater in a hydrogen atmosphere, converting low-value-added chloropropane glycol into high-value-added 1,2-propanediol (hereinafter referred to as propylene glycol). Propylene glycol is an important raw material for unsaturated polyesters, epoxy resins, polyurethane resins, plasticizers, and surfactants, and has wide applications in the chemical, food, and pharmaceutical industries. The method disclosed herein can obtain higher-value propylene glycol products while processing chloropropanediol, reducing the processing cost of chloropropanediol and thus improving the techno-economic efficiency of the hydroperoxide-based epichlorohydrin production process.

[0019] In one embodiment, the content of the active metal component is 0.1 to 15% 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.

[0020] In a preferred embodiment, the content of the active metal component is 0.7-10% 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 and the selectivity of propylene glycol can be further improved.

[0021] In one specific embodiment, the BET specific surface area of ​​the hydrodechlorination catalyst is 1000~2000 m². 2 / g, preferably 1500~2000 m 2 / g; the particle size is 10~200 mesh, preferably 30~120 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.

[0022] In one specific embodiment, the hydrodechlorination catalyst is prepared by a method comprising the following steps: (1) The activated carbon support is impregnated with an active metal precursor solution and then dried to obtain a catalyst precursor; optionally, the active metal precursor includes RuCl3; (2) The catalyst precursor is calcined and reduced under hydrogen conditions.

[0023] In one specific embodiment, in step (1), the Ru in the active metal precursor solution... 3+ The concentration is 0.05~7.5% by weight, preferably 0.35~5.0% by weight. Preferably, the impregnation treatment is an equal-volume impregnation, which can be carried out using conventional operations; wherein the impregnation temperature can be 20~30℃, and the impregnation time can be 10~15h; Optionally, the drying conditions include: a drying temperature of 100~120℃ and a drying time of 6~10h.

[0024] 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.

[0025] 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 chloropropane glycol is 0.1-4% by weight, preferably 0.1-1.8% by weight. The method provided in this embodiment effectively removes chloropropane glycol from epichlorohydrin wastewater within a wide range of concentrations and has a wide range of applications.

[0026] 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.

[0027] In one embodiment, in the catalytic 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.

[0028] In one embodiment, the conditions for the catalytic hydrodechlorination reaction include: a reaction temperature of 120-220°C, a reaction time of 1-10 hours, and a hydrogen pressure of 5-100 bar. The conditions for the catalytic hydrodechlorination reaction provided in this embodiment can effectively remove chloropropane glycol from epichlorohydrin wastewater.

[0029] In a preferred embodiment, the conditions for the catalytic hydrodechlorination reaction include: a reaction temperature of 160-200°C, a reaction time of 1-5 hours, and a hydrogen pressure of 5-60 bar. The preferred catalytic hydrodechlorination reaction conditions provided by this embodiment can further improve the removal efficiency of chloropropane glycol from epichlorohydrin wastewater.

[0030] According to this disclosure, the hydrogenation and dechlorination reaction of chloropropanediol 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.

[0031] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0032] The content of active metal components in the catalyst was obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES). The BET specific surface area of ​​the catalyst was obtained by static capacity adsorption analysis.

[0033] The particle size of the catalyst is controlled by the mesh size of the sieve used for sieving.

[0034] After the hydrodechlorination reaction of chloropropane glycol is completed, the concentrations of chloropropane glycol and propylene glycol in the epichlorohydrin wastewater before and after the reaction can be analyzed by gas chromatography (Agilent 6890N), thereby calculating the chloropropane glycol conversion rate and propylene glycol selectivity.

[0035] Wherein, the conversion rate of chloropropanediol (%) = (initial concentration of chloropropanediol - concentration of chloropropanediol after reaction) / initial concentration of chloropropanediol × 100%; Propylene glycol selectivity (%) = propylene glycol molar concentration / (initial molar concentration of chloropropanediol - molar concentration of chloropropanediol after reaction) × 100%.

[0036] 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 based on the total weight of the hydrodechlorination catalyst, the content of the active metal component Ru is 0.7% by weight. The specific steps include: First, the equivalent water absorption capacity of 1 gram of activated carbon was measured to be 2 grams; then, 0.0145 grams of RuCl3 was added to 2 grams of water to obtain a RuCl3 aqueous solution (active metal precursor solution, Ru...). 3+ A catalyst precursor was prepared by impregnation of 0.35% by weight and 1 gram of activated carbon (30 mesh) in equal amounts, with an impregnation temperature of 30°C and an impregnation time of 12 h. The catalyst precursor was dried and then calcined and reduced in a hydrogen atmosphere to obtain the catalyst, with a drying temperature of 110°C and a drying time of 6 h. The calcination and reduction temperature was 500°C and the calcination and reduction time was 4 h, with a hydrogen flow rate of 40 mL / min.

[0037] Preparation of 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 based on the total weight of the hydrodechlorination catalyst, the content of the active metal component Pd was 0.7% by weight. This comparative example followed the method in Preparation Example 1, except that the active metal precursor was replaced with 0.0118 g of PdCl2, which was added to 2 g of water to obtain a PdCl2 aqueous solution (active metal precursor solution, Pd...). 2+ (The concentration was 0.35% by weight), and the rest of the process was the same as in Preparation Example 1.

[0038] Preparation of 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 based on the total weight of the hydrodechlorination catalyst, the content of the active metal component Pt was 0.7% by weight. This comparative example followed the method in Preparation Example 1, except that the active metal precursor was replaced with 0.0148 g of H2PtCl6, and 2 g of water was added to obtain an aqueous solution of H2PtCl6 (active metal precursor solution, Pt). 4+ (The concentration was 0.35% by weight), and the rest of the process was the same as in Preparation Example 1.

[0039] Preparation Example 2 This preparation example is 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 includes Ru, and the content of Ru in the active metal component is 2% by weight based on the total weight of the hydrodechlorination catalyst. The specific steps include: The method described in Preparation Example 1 differs from that in that 0.0419 g of RuCl3 is added to 2 g of water to obtain an aqueous solution of RuCl3 (an active metal precursor solution, Ru...). 3+ (The concentration was 1.00% by weight), and the rest of the process was the same as in Preparation Example 1.

[0040] Preparation Example 3 This preparation example is 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 includes Ru, and the content of Ru in the active metal component is 4% by weight based on the total weight of the hydrodechlorination catalyst. The specific steps include: The method described in Preparation Example 1 differs from that in that 0.0885 g of RuCl3 is added to 2 g of water to obtain an aqueous solution of RuCl3 (an active metal precursor solution, Ru...). 3+ (The concentration was 2.00% by weight), and the rest of the process was the same as in Preparation Example 1.

[0041] Preparation Example 4 This preparation example is 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 includes Ru, and the content of Ru in the active metal component is 10% by weight based on the total weight of the hydrodechlorination catalyst. The specific steps include: The method described in Preparation Example 1 differs from that in that 0.2280 g of RuCl3 is added to 2 g of water to obtain an aqueous solution of RuCl3 (an active metal precursor solution, Ru...). 3+ The concentration was 4.99% by weight), and the rest of the process was the same as in Preparation Example 1.

[0042] Preparation Example 5 This preparation example is 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 includes Ru, and the content of Ru in the active metal component is 0.1% by weight based on the total weight of the hydrodechlorination catalyst. The specific steps include: The method described in Preparation Example 1 differs from that in that 0.0021 g of RuCl3 is added to 2 g of water to obtain an aqueous solution of RuCl3 (an active metal precursor solution, Ru...). 3+ (The concentration is 0.05% by weight), and the rest of the process is the same as in Preparation Example 1.

[0043] Preparation Example 6 This preparation example is 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 includes Ru, and based on the total weight of the hydrodechlorination catalyst, the content of the active metal component Ru is 15% by weight, specifically including the following steps: The method described in Preparation Example 1 differs from that in that 0.3622 g of RuCl3 is added to 2 g of water to obtain an aqueous solution of RuCl3 (an active metal precursor solution, Ru...). 3+ The concentration was 7.47% by weight), and the rest of the process was the same as in Preparation Example 1.

[0044] Preparation Example 7 This preparation example uses the same method as in Preparation Example 1 to prepare catalyst C7, but differs from Preparation Example 1 in that: The calcination and reduction temperature was 800℃, the calcination and reduction time was 2h, and the hydrogen flow rate was 100 mL / min. The remaining processes were the same as in Preparation Example 1, to prepare a hydrodechlorination catalyst (Ru / C catalyst, denoted as C7), 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 0.7% by weight based on the total weight of the hydrodechlorination catalyst.

[0045] The active metal content and structural characteristic parameters of the catalysts obtained from the above preparation examples and comparative examples are listed in Table 1 below.

[0046] Table 1

[0047] In the above preparation examples and comparative examples, the catalysts were all sieved using a 30-mesh sieve.

[0048] The following examples illustrate the catalytic effect of the catalysts obtained from the above preparation examples and comparative examples in the reaction of removing chloropropane glycol from epichlorohydrin wastewater.

[0049] Example 1 50 g of epichlorohydrin wastewater (50 wt% methanol, 0.136 wt% chloropropane glycol, and the remainder water) was added to a 100 mL Hastelloy reactor. 0.3 g of the Ru / C hydrodechlorination catalyst C1 (0.5 wt% Ru) from Preparation Example 1 was added, with a weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst of 100:0.6. The catalytic hydrodechlorination reaction was carried out under a hydrogen atmosphere. The reaction conditions were: 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 of chloropropane glycol and the selectivity of propylene glycol were calculated, and the test results are listed in Table 2.

[0050] Comparative Example 1 This comparative example follows the method in Example 1, except that the catalyst is replaced with the catalyst D1 obtained in the preparation of Comparative Example 1.

[0051] Comparative Example 2 This comparative example follows the method in Example 1, except that the catalyst is replaced with the catalyst D2 obtained in the preparation of Comparative Example 2.

[0052] Example 2 This embodiment refers to the method in Embodiment 1, except that the reaction temperature is increased to 180°C. The rest of the process is the same as in Embodiment 1. The test results are listed in Table 2.

[0053] Example 3 This embodiment refers to the method in Embodiment 1, except that the reaction temperature is increased to 200°C. The rest of the process is the same as in Embodiment 1. The test results are listed in Table 2.

[0054] Example 4 This embodiment 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.

[0055] Example 5 This embodiment refers to the method in Example 2, except that the Ru / C hydrodechlorination catalyst C3 (Ru content is 4% by weight) in Preparation Example 3 is used. The rest of the process is the same as in Example 2. The test results are listed in Table 2.

[0056] Example 6 This embodiment refers to the method in Example 2, except that the Ru / C hydrodechlorination catalyst C4 (Ru content is 10% by weight) in Preparation Example 4 is used. The rest of the process is the same as in Example 2. The test results are listed in Table 2.

[0057] Example 7 This embodiment refers to the method in Example 6, except that the concentration of chloropropane glycol in the epichlorohydrin wastewater is increased to 0.503% by weight. The rest of the process is the same as in Example 6. The test results are listed in Table 2.

[0058] Example 8 This embodiment refers to the method in Example 6, except that the concentration of chloropropane glycol in the epichlorohydrin wastewater is increased to 1.04% by weight. The rest of the process is the same as in Example 6. The test results are listed in Table 2.

[0059] Example 9 This embodiment refers to the method in Example 6, except that the concentration of chloropropane glycol in the epichlorohydrin wastewater is increased to 1.76% by weight. The rest of the process is the same as in Example 6. The test results are listed in Table 2.

[0060] Example 10 This embodiment refers to the method in embodiment 9, except that the reaction time is extended to 2 hours. The rest of the process is the same as in embodiment 9. The test results are listed in Table 2.

[0061] Example 11 This embodiment refers to the method in embodiment 9, except that the reaction time is extended to 4 hours. The rest of the process is the same as in embodiment 9. The test results are listed in Table 2.

[0062] Example 12 This embodiment refers to the method in Example 1, except that the catalyst is replaced with the catalyst C5 obtained in Preparation Example 5 (Ru content is 0.1% by weight).

[0063] Example 13 This embodiment refers to the method in Example 1, except that the catalyst is replaced with the catalyst C6 (Ru content is 15% by weight) obtained in Preparation Example 6.

[0064] Example 14 This embodiment refers to the catalytic reaction method in Example 1, but differs from Example 1 in that: Add 4g of catalyst C1 to 50g of epichlorohydrin wastewater. The weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst is 100:8. The rest of the process is the same as in Example 1.

[0065] Example 15 This embodiment refers to the catalytic reaction method in Example 1, but differs from Example 1 in that: The reaction temperature was adjusted to 220°C and the reaction time was 10 hours. The rest of the process was the same as in Example 1.

[0066] The chloropropanediol conversion and propylene glycol selectivity obtained from the above examples and comparative examples are listed in Table 2 below. Table 2

[0067] The data in Table 2 shows that: In Comparative Examples 1 and 2, the types of active metal components were changed, resulting in extremely low chloropropane glycol conversion rates and the inability to generate propylene glycol in the reaction of removing chloropropane glycol from epichlorohydrin wastewater. Therefore, it can be seen that only by using the method and catalyst disclosed herein can chloropropane glycol be effectively removed from epichlorohydrin wastewater and high-value-added propylene glycol products be generated.

[0068] A comparison of Examples 1-3 shows that increasing the reaction temperature can improve the conversion rate of chloropropanediol, but the selectivity of the target product propylene glycol decreases. A comparison of Examples 9 and Examples 10-11 shows that increasing the reaction time significantly increases the conversion rate of chloropropanediol, but the selectivity of the target product propylene glycol decreases slowly. A comparison of Examples 1-3, Examples 9-11 and Example 15 shows that in Example 15, after further increasing the reaction temperature and reaction time, although chloropropanediol is completely converted, the selectivity of the target propylene glycol decreases significantly. At this time, more by-products are generated, and the energy consumption is high under these reaction conditions. This indicates that the catalytic hydrodechlorination reaction conditions in Examples 1-3 and 9-11 are within the preferred range provided in this disclosure. Examples 1-3 can balance the conversion rate of chloropropanediol and the selectivity of propylene glycol.

[0069] A comparison of Examples 2 and 4-6 shows that increasing the active center loading can slowly increase the conversion rate of chloropropanediol and significantly improve the selectivity of the target product propylene glycol. A comparison of Examples 1 and 12-13 shows that when the catalyst active center loading is too low (catalyst C5), both the conversion rate of chloropropanediol and the selectivity of the target product propylene glycol are low. When the loading is too high (catalyst C6), although the conversion rate of chloropropanediol and the selectivity of the target product propylene glycol can be greatly improved, the excessive loading will lead to increased catalyst cost, darken the color of the reaction solution, and show obvious loss of catalyst active centers. This indicates that when the active metal content in the catalyst is within the preferred range provided in this disclosure, it has a better effect.

[0070] A comparison of Examples 6 and 7-9 shows that increasing the concentration of the reactant chloropropanediol gradually decreases its conversion rate and propylene glycol selectivity. When the concentration of the reactant chloropropanediol is within the preferred range provided in this disclosure, a better hydrodechlorination effect can be achieved.

[0071] A comparison of Examples 1 and 14 shows that increasing the amount of catalyst used can improve the conversion rate of chloropropane glycol and the selectivity of the target product propylene glycol. However, excessive use not only increases the cost of catalyst use but also affects the external diffusion mass transfer effect of the catalyst. This indicates that in Example 1, the hydrodechlorination reaction was carried out according to the weight ratio of epichlorohydrin wastewater to hydrodechlorination catalyst provided in this disclosure, and the catalyst per unit mass had a better reaction effect.

[0072] A comparison of Example 1 and Example 16 shows that increasing the catalyst calcination and reduction temperature leads to a decrease in catalyst activity. The catalyst prepared in Example 1 using the preferred preparation conditions provided in this disclosure has a better catalytic hydrogenation and dechlorination effect.

[0073] 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.

[0074] 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.

[0075] 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 chloropropane glycol 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 catalytic hydrodechlorination reaction, thereby converting chloropropane glycol in the epichlorohydrin wastewater into propylene glycol; 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 0.1-15% by weight, preferably 0.7-10% by weight.

3. The method according to claim 1, characterized in that, The BET specific surface area of ​​the hydrodechlorination catalyst is 1000~2000 m². 2 / g, preferably 1500~2000 m 2 / g; particle size is 10~200 mesh, preferably 30~120 mesh.

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

5. The method according to claim 4, characterized in that, In step (1), Ru in the active metal precursor solution 3 + The concentration is 0.05~7.5% by weight, preferably 0.35~5.0% by weight. Preferably, the impregnation treatment is an equal-volume impregnation; The immersion temperature is 20~30℃, and the immersion time is 10~15h; Optionally, the drying conditions include: a drying temperature of 100~120℃ and a drying time of 6~10h; Optionally, in step (2), the conditions for the calcination reduction treatment 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.

6. The method according to claim 1, characterized in that, The epichlorohydrin wastewater comes from the reaction of 3-chloropropene with hydrogen peroxide to synthesize epichlorohydrin. Optionally, based on the total weight of the epichlorohydrin wastewater, the content of chloropropanediol is 0.1 to 4% by weight, preferably 0.1 to 1.8% by weight.

7. 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.

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

9. The method according to claim 1, characterized in that, The conditions for the catalytic hydrodechlorination reaction include: a reaction temperature of 120~220℃, a reaction time of 1~10h, and a hydrogen pressure of 5~100bar.

10. The method according to claim 9, characterized in that, The conditions for the catalytic hydrodechlorination reaction include: a reaction temperature of 160~200℃, a reaction time of 1~5h, and a hydrogen pressure of 5~60bar.

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