Method for separating and recovering propylene glycol ether and propylene glycol from wastewater containing alcohol ether

Abstract

The invention relates to a method for recovering propylene glycol and propylene glycol methyl ether from alcohol ether wastewater, which is characterized by comprising the following steps of: a, mixing the alcohol ether wastewater with an extracting agent, and separating to obtain a heavy phase and a light phase; b, separating the heavy phase obtained in the step a to obtain a product containing propylene glycol and / or propylene glycol ether; the extraction agent comprises halogenated alcohol. The method is simple, efficient, convenient to operate, low in energy consumption, high in yield and purity of propylene glycol and propylene glycol ether and suitable for large-scale production.

Description

A method for separating and recovering propylene glycol ethers and propylene glycol from alcohol-ether-containing wastewater Technical Field

[0001] This invention relates to a method for separating and recovering propylene glycol ethers and propylene glycol from alcohol-ether-containing wastewater. Background Technology

[0002] In methanol solvent, a titanium-silicon molecular sieve catalyst catalyzes the reaction of propylene and hydrogen peroxide to produce propylene oxide and water. After separation and purification, propylene oxide is obtained. Since propylene oxide reacts with water to produce propylene glycol, and simultaneously reacts with methanol to produce propylene glycol ethers, including two isomers, 1-methoxy-2-propanol and 2-methoxy-1-propanol, these byproducts enter the wastewater, generating wastewater containing propylene glycol and propylene glycol ethers.

[0003] Ethers are biotoxic and difficult to treat biochemically, posing challenges to the treatment of wastewater from propylene oxide plants. Separating propylene glycol ethers from the wastewater can improve its treatability and yield higher-value propylene glycol ethers, thus enhancing the plant's economics. However, propylene glycol ethers are azeotropic with water, and direct distillation only yields the ether-water azeotrope. Therefore, current methods typically use an azeotropic agent to first separate water and propylene glycol ethers through azeotropic distillation, then separate the azeotropic agent from the water, allowing the azeotropic agent to be recycled.

[0004] CN110606799A discloses a byproduct recovery system and method for the HPPO process in the production of propylene oxide, including an evaporation unit, a propylene glycol recovery unit, and a propylene glycol methyl ether recovery unit; the evaporation unit includes at least two stages of evaporation devices connected in sequence; the propylene glycol recovery unit includes at least two stages of distillation columns connected in sequence; the propylene glycol methyl ether recovery unit includes a methanol removal device, a concentration device, an extraction device, an extraction recovery device, a dehydration device, and a separation device connected in sequence, and the exhaust port of the evaporation unit is connected to the feed port of the methanol removal device.

[0005] CN118359486A discloses a method for recovering propylene glycol ether. The method includes: (1) introducing wastewater containing propylene glycol ether into a first separation tower for first distillation separation; and (2) introducing the overhead vapor from the first separation tower in step (1) into a second separation tower for second distillation separation. This method achieves direct distillation separation of propylene glycol ether and water in the absence of an azeotropic agent, obtaining high-purity propylene glycol ether.

[0006] CN113072432A discloses a method for recovering alcohols and ethers from propylene oxide wastewater, comprising: introducing propylene oxide wastewater into an ether concentration tower for ether concentration treatment; using the mixture I obtained at the top of the ether concentration tower as a heat source for the reboiler of the alcohol dehydration tower and then introducing it into the dehydration tower for post-treatment; and using the mixture II obtained at the top of the alcohol dehydration tower as a heat source for the reboiler of the dehydration tower.

[0007] CN113072427A discloses a method for recovering propylene glycol ethers and propylene glycol, comprising: (1) introducing organic wastewater containing propylene glycol ethers and propylene glycol into an ether concentration tower for distillation separation to obtain a first overhead stream and a first bottom stream; (21) introducing the first overhead stream into a dehydration tower for propylene glycol ether compound recovery treatment; and (22) introducing the first bottom stream into a propylene glycol concentration tower for propylene glycol concentration treatment.

[0008] CN113072116A discloses a method for treating propylene oxide wastewater, comprising: (1) introducing organic wastewater into an alcohol concentration tower for concentration, collecting a portion of the bottom liquid of the alcohol concentration tower as a concentrated alcohol organic matter extract, and introducing at least a portion of the bottom liquid into the reboiler of the alcohol concentration tower for circulating heating; (2) pressurizing and compressing the overhead gas of the alcohol concentration tower to obtain mixture I, and then introducing mixture I as a heat source into the reboiler of the alcohol concentration tower for heat exchange to obtain mixture II; (3) recycling a portion of mixture II back to the alcohol concentration tower for distillation separation. The optimized thermal coupling method enables the recovery of alcohol organic matter from propylene oxide wastewater.

[0009] Existing technologies all require energy-intensive operations such as multi-step evaporation and concentration of alcohol and ether wastewater and distillation separation, resulting in long processes and high energy consumption. Summary of the Invention

[0010] The purpose of this invention is to provide a method for recovering propylene glycol and propylene glycol ether from alcohol ether wastewater, thereby reducing the difficulty of wastewater treatment. This method has a simple process flow, is easy to operate, allows for easy separation of extractant components, has low energy consumption, and produces high yields and purity of propylene glycol and propylene glycol ether, making it suitable for large-scale production.

[0011] To achieve the above objectives, the present invention provides a method for recovering propylene glycol and propylene glycol methyl ether from alcohol ether wastewater, characterized in that the method comprises: step a: mixing alcohol ether wastewater with an extractant and then performing extraction separation to obtain a heavy phase and a light phase; and step b: separating the heavy phase obtained in step a to obtain a product containing propylene glycol and / or propylene glycol methyl ether; wherein the extractant comprises a haloalcohol.

[0012] Preferably, the present invention is used to treat alcohol and ether wastewater generated from propylene oxide plants or experiments.

[0013] Preferably, in the alcohol and ether wastewater treated in this invention, the mass fraction of alcohols and / or ethers is preferably not less than 0.1%. More specifically, the alcohols include one or more of propylene glycol, ethylene glycol, dipropylene glycol, tripropylene glycol, and glycerol; and the ethers include one or more of 1-methoxy-2-propanol and 2-methoxy-1-propanol.

[0014] Preferably, the solubility of the haloalcohol in water is not less than 1 g / 100 g.

[0015] Preferably, the haloalcohol has m carbon atoms, where m is preferably a positive integer from 1 to 12, and the halogen element, hydroxyl group and hydrogen are bonded to the carbon atoms. The halogen element can be one or more of fluorine, chlorine, bromine and iodine, and its number does not exceed 2m+1. The number of hydroxyl groups does not exceed 5. The preferred halogen is fluorine.

[0016] Preferably, the haloalcohol may be 2,2,3,3-tetrafluoropropanol (76-37-9), 1H,1H-pentafluoropropanol (422-05-9), 3-fluoropropanol (462-43-1), hexafluoroisopropanol (920-66-1), 2-allylic hexafluoroisopropanol (646-97-9), 1,3-difluoro-2-propanol (453-13-4), hexafluoro-2-methylisopropanol (1515-14-6), perfluorotert-butanol (2378-02-1), 2-trifluoro One or more of the following: methyl-2-propanol (507-52-8), 2,2-bis(trifluoromethyl)propanol (2927-17-5), 2,2-difluoropropanol (33420-52-9), 1-(4-fluoropropoxy)-2-propanol (307532-03-2), 1,1,1-trifluoro-2-propanol (374-01-6), 3,3,3-trifluoro-1-propanol (2240-88-2), and 2-vinylhexafluoroisopropanol (19701-19-0).

[0017] Preferably, the mixing in step a can be performed intermittently or continuously.

[0018] Preferably, the separation in step a can be settling, sedimentation, centrifugation, or decantation.

[0019] Preferably, the weight ratio of the alcohol ether wastewater to the extractant is 1:(0.01-10).

[0020] Preferably, the mixing in step a is carried out at 5–80°C and at atmospheric pressure to 2 MPa (gauge pressure).

[0021] Preferably, the separation described in step b can be distillation or rectification, and can be a continuous or intermittent operation. It can be a single separation unit or a combination of multiple separation units.

[0022] Preferably, the process may further include using part or all of the extractant obtained from the heavy phase in step b for repeating the mixing and separation process in step a.

[0023] The method provided by this invention uses an organic extractant to extract and separate alcohol-ether-containing wastewater. This yields high-purity propylene glycol and propylene glycol ether products while reducing the difficulty and cost of wastewater treatment. The method features a simple process flow, convenient operation, easy separation of extractant components, low energy consumption, and high yields and purity of propylene glycol and propylene glycol ethers, making it suitable for large-scale production. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0025] Figure 1 is a schematic diagram of an optional extraction and separation process of the present invention, wherein A is an extraction tower, 1 and 2 are optional inlets for alcohol ether wastewater and extractant, respectively, and 3 and 4 are optional outlets for light phase and heavy phase, respectively.

[0026] Figure 2 is a schematic diagram of the optional heavy phase distillation separation process of the present invention, wherein B is the distillation column, 5 is the optional heavy phase feed inlet, and 6 and 7 are the optional extractant phase and product outlet, respectively. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0028] The purpose of this invention is to provide a method for separating alcohol-ether-containing wastewater. This method has a simple process flow, is easy to operate, allows for easy separation of extractant components, has low energy consumption, and produces high yields and purity of propylene glycol and propylene glycol ether, making it suitable for large-scale production.

[0029] To achieve the above objectives, the present invention provides a method for recovering propylene glycol and propylene glycol methyl ether from alcohol ether wastewater, characterized in that the method comprises: step a: mixing alcohol ether wastewater with an extractant and then performing extraction separation to obtain a heavy phase and a light phase; and step b: separating the heavy phase obtained in step a to obtain a product containing propylene glycol and / or propylene glycol methyl ether; wherein the extractant comprises a haloalcohol.

[0030] According to the method of the present invention, the alcohol ether wastewater may be any aqueous solution containing propylene glycol and / or propylene glycol ether (one or more of 1-methoxy-2-propanol and 2-methoxy-1-propanol), preferably alcohol ether wastewater generated in a propylene oxide production device or during an experiment, and more preferably alcohol ether wastewater generated in a device for producing propylene oxide by propylene hydrogen peroxide oxidation.

[0031] According to the method of the present invention, there are no special requirements for the content of alcohols and / or ethers in the alcohol ether wastewater. For example, the mass fraction of alcohols and / or ethers is preferably not less than 0.1%, more preferably not less than 1%. There is no upper limit requirement for the concentration of alcohols and / or ethers in the alcohol ether wastewater of the present invention, but generally, the concentration of alcohols and / or ethers in the wastewater will not be too high. Therefore, the mass fraction of alcohols and / or ethers in the present invention can be no higher than 30%, no higher than 20%, or no higher than 10%.

[0032] According to the method of the present invention, the alcoholic organic compounds include one or more selected from propylene glycol, ethylene glycol, dipropylene glycol, tripropylene glycol, and glycerol; the etheric organic compounds include one or more selected from 1-methoxy-2-propanol and 2-methoxy-1-propanol. Optionally, the alcohol-ether wastewater may also contain small amounts of monohydric alcohols, aldehydes, ketones, and inorganic salts as impurities; the present invention does not have any special requirements for this.

[0033] According to the method of the present invention, there are no special requirements for the solubility of the haloalcohol; it can be readily soluble, soluble, slightly soluble, or insoluble in water. To better achieve the extraction effect, according to the method of the present invention, the haloalcohol preferably has a solubility in water (20°C, 1 atm) of not less than 1 g / 100 g. For example, 2,3-dichloro-1-propanol has a solubility of 12 g / 100 g in water, hexafluoroisopropanol has a solubility of 100 g / 100 g in water, and tetrafluoropropanol, 2,2,3,3-tetrafluoropropanol, perfluorotert-butanol, and hexafluoroisopropanol all have solubilities in water > 1 g / 100 g.

[0034] The extractant used in this invention possesses unique physical properties, making it particularly suitable for separating liquid products containing propylene glycol and / or propylene glycol ethers. The extractant used in this invention effectively separates propylene glycol and propylene glycol ethers, but also readily separates from its aqueous solution to form a heavy phase rich in propylene glycol, propylene glycol ethers, and the extractant, and a light phase rich in water. Further separation of the heavy phase yields the extractant, propylene glycol, and propylene glycol ethers. The extractant of this invention has a low boiling point and low molar heat of vaporization, resulting in low energy consumption during the further separation of the heavy phase.

[0035] According to the method of the present invention, the haloalcohol has m carbon atoms, where m is preferably a positive integer from 1 to 12, more preferably 2 to 8, and more preferably 3 to 6. In the haloalcohol, a halogen element, a hydroxyl group, and hydrogen are bonded to carbon atoms. The halogen element can be one or more of fluorine, chlorine, bromine, and iodine, preferably one or more of fluorine and chlorine, and more preferably fluorine. The number of halogens in the haloalcohol molecule does not exceed 2m+1, and the number of hydroxyl groups does not exceed 5, preferably not more than 3, and more preferably 1. Atoms in the haloalcohol molecule can be substituted with their isotopes.

[0036] According to the method of the present invention, the carbon atom of the haloalcohol can be saturated carbon or unsaturated carbon, that is, the haloalcohol molecule can contain unsaturated chemical bonds such as double bonds, triple bonds, and benzene rings.

[0037] According to the method of the present invention, the haloalcohol may be 2-fluoroethanol (371-62-0), trifluoroethanol (75-89-8), 1-chloro-2-propanol (127-00-4), 3-chloro-1-propanol (627-30-5), 2-chloro-1-propanol (78-89-7), 1,3-dichloropropanol (96-23-1), 2,3-dichloro-1-propanol (616-23-9), bromopropanol (627-18-9), 2,2,3,3-tetrafluoropropanol (76-37-9), 1H,1H-pentafluoropropanol (422-05-9), 3-fluoropropanol (462-43-1), hexafluoroisopropanol (920-66-1), 1,1,1,3,3,3-hexafluoropropanol. 2-Deuterated propanol (38701-74-5), 2-allyl hexafluoroisopropanol (646-97-9), 1,3-difluoro-2-propanol (453-13-4), hexafluoro-2-methylisopropanol (1515-14-6), perfluorotert-butanol (2378-02-1), 1-chloro-3-fluoro-2-propanol (453-11-2), 3-bromo-1,1,1-trifluoro-2-propanol (431-34-5), 2-trifluoromethyl-2-propanol (507-52-8), 2,2-bis(trifluoromethyl)propanol (2927-17-5), 2,2-difluoropropanol (33420-52-9), 3-bromo-trifluoro-2-propanol (88378-50-1), 1,1,1 3,3,3-Hexafluoro-2-phenyl-2-propanol (718-64-9), 3-(3-trifluoromethylphenyl)propanol (78573-45-2), 2-(4-fluorophenyl)-2-propanol (402-41-5), 2-[3,5-(bistrifluoromethyl)phenyl]2-propanol (28180-47-4), 1,3-bis(1,1,1,3,3,3-hexafluoro-2-propanol)benzene (802-93-7), 3-perfluorooctylpropanol (1651-41-8), 3-(perfluorohexyl)propanol (80806-68-4), (R)-(+)-1-chloro-3-(4-fluorophenoxy)-2-propanol (307532-04-3), 1-(4-fluoropropoxy)- One or more of the following: 2-propanol (307532-03-2), 1,1,1-trifluoro-2-propanol (374-01-6), 3,3,3-trifluoro-1-propanol (2240-88-2), 2-vinylhexafluoroisopropanol (19701-19-0), 2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoro-2-propanol (722-92-9), hexafluoro-2-(p-tolyl)isopropanol (2010-61-9), 1-(4-trifluoromethylphenyl)-1-propanol (67081-98-5), 3-perfluorobutyl-2-propanol (80233-96-1), and 3-(perfluoro-7-methylhexyl)-2-iodopropanol (65726-35-4).

[0038] Preferably, the haloalcohol may be 1-chloro-2-propanol (127-00-4), 3-chloro-1-propanol (627-30-5), 2-chloro-1-propanol (78-89-7), 1,3-dichloropropanol (96-23-1), 2,3-dichloro-1-propanol (616-23-9), bromopropanol (627-18-9), or 2,2,3,3-tetrafluoropropanol (76- 37-9), 1H,1H-pentafluoropropanol (422-05-9), 3-fluoropropanol (462-43-1), hexafluoroisopropanol (920-66-1), 1,1,1,3,3,3-hexafluoro-2-deuterated propanol (38701-74-5), 2-allylic hexafluoroisopropanol (646-97-9), 1,3-difluoro-2-propanol (453-13-4), hexafluoro-2- Methyl isopropanol (1515-14-6), perfluorotert-butanol (2378-02-1), 1-chloro-3-fluoro-2-propanol (453-11-2), 2-trifluoromethyl-2-propanol (507-52-8), 2,2-bis(trifluoromethyl)propanol (2927-17-5), 2,2-difluoropropanol (33420-52-9), 3-bromo-trifluoro-2-propanol (8837) One or more of the following: 8-50-1), 1-(4-fluoropropoxy)-2-propanol (307532-03-2), 1,1,1-trifluoro-2-propanol (374-01-6), 3,3,3-trifluoro-1-propanol (2240-88-2), 2-vinylhexafluoroisopropanol (19701-19-0), and 3-perfluorobutyl-2-propanol (80233-96-1).

[0039] More preferably, the haloalcohol may be 2,2,3,3-tetrafluoropropanol (76-37-9), 1H,1H-pentafluoropropanol (422-05-9), 3-fluoropropanol (462-43-1), hexafluoroisopropanol (920-66-1), 2-allylic hexafluoroisopropanol (646-97-9), 1,3-difluoro-2-propanol (453-13-4), hexafluoro-2-methylisopropanol (1515-14-6), perfluorotert-butanol (2378-02-1), 2-trifluoropropanol, etc. One or more of the following: fluoromethyl-2-propanol (507-52-8), 2,2-bis(trifluoromethyl)propanol (2927-17-5), 2,2-difluoropropanol (33420-52-9), 1-(4-fluoropropoxy)-2-propanol (307532-03-2), 1,1,1-trifluoro-2-propanol (374-01-6), 3,3,3-trifluoro-1-propanol (2240-88-2), and 2-vinylhexafluoroisopropanol (19701-19-0).

[0040] According to the method of the present invention, the mixing in step a can be performed intermittently or continuously, and the separation in step a can be achieved through settling, sedimentation, centrifugation, or decantation. The present invention does not impose particular limitations on the operating method and equipment used in the extraction process; it can be a single or multiple intermittent extraction separation, or a continuous extraction separation. It can be carried out in ordinary containers, stirred tanks, microchannel reactors, tubular reactors, centrifugal reactors, or extraction towers, such as rotating disc towers, packed towers, or sieve plate towers. Various extraction devices may or may not have internal components. Considering the convenience of industrial applications and the reduction of harm to operators from organic vapors, a continuous extraction separation operation and extraction separation operations performed in an extraction tower are preferred. The extraction tower preferably has 1 to 30 theoretical plates.

[0041] To achieve good extraction and separation results, a certain amount of extractant is required. Too little extractant leads to incomplete extraction, while too much extractant results in high energy consumption. According to the method of the present invention, preferably, the weight ratio of the alcohol ether wastewater to the extractant is 1:(0.01-10), more preferably 1:(0.05-5), even more preferably 1:(0.1-1), still more preferably 1:(0.15-0.8), and most preferably 1:(0.2-0.5).

[0042] The present invention does not impose any particular restrictions on the extraction conditions. Preferably, the mixing in step a is carried out at 5-80°C and atmospheric pressure to 2MPa (gauge pressure), and more preferably at 20-60°C and atmospheric pressure to 0.5MPa.

[0043] According to the method of the present invention, preferably, the separation in step b can be distillation or rectification, which can be continuous or intermittent operation, and can be a single separation unit or a combination of multiple separation units. For example, a distillation column can be used to separate the extractant from the heavy phase obtained in step a to obtain propylene glycol and propylene glycol ether products. Alternatively, the propylene glycol and propylene glycol ether can be further distilled to obtain propylene glycol and propylene glycol ether products respectively. Another option is to use a distillation column to separate the extractant and propylene glycol ether product at the top of the column and the propylene glycol product at the bottom of the column from the heavy phase obtained in step a, and then further distill the product at the top of the column to obtain the extractant and propylene glycol ether products. In the above schemes, the propylene glycol ether product can also be separated to obtain 1-methoxy-2-propanol and 2-methoxy-1-propanol. The present invention has no limitations on any reasonable and feasible combination. The distillation or rectification can be intermittent or continuous operation, and a distillation kettle, plate column, or packed column can be used as the distillation equipment; the present invention has no special limitations. Distillation separation is prior art and will not be described in detail in the present invention.

[0044] According to the method of the present invention, optionally, it may further include using part or all of the heavy phase obtained in step b after separating the extractant for repeating the mixing and separation process of step a.

[0045] Through the above technical solution, the present invention provides a simple method for separating high-purity propylene glycol and / or propylene glycol ethers from alcohol-ether-containing wastewater using an extractant. The method of the present invention has the following positive effects:

[0046] 1. The process is simple; the raw materials are directly separated by distillation after extraction, requiring no special equipment and making operation convenient.

[0047] 2. The extractant has simple components, is easy to separate from other components in the raw material, has low separation energy consumption, and the separated extractant can be recycled for extraction.

[0048] 3. The method of the present invention has high yield and product purity of propylene glycol and / or propylene glycol ether.

[0049] Unless otherwise specified, all raw materials used in the examples are chemically pure reagents.

[0050] The reaction products were analyzed by gas chromatography. The chromatographic conditions were as follows: Agilent-7890 chromatograph, HP-INNOWAX capillary column, injection volume 1 μL, injection port temperature 280℃. Column temperature was maintained at 50℃ for 5 min, then increased to 250℃ at a rate of 10℃ / min and held for 25 min. An FID detector was used, with a detector temperature of 300℃.

[0051] In the various embodiments and comparative examples:

[0052] Propylene glycol yield = (Mass of propylene glycol in the product separated in step b) / (Mass of propylene glycol in the alcohol ether wastewater) × 100%

[0053] Propylene glycol purity = (Cyclical peak area of ​​propylene glycol in the product separated in step b) / (Area of ​​all peaks) × 100%

[0054] 1-Methoxy-2-propanol yield = (Mass of 1-methoxy-2-propanol in the product separated in step b) / (Mass of 1-methoxy-2-propanol in the alcohol ether wastewater) × 100%

[0055] Purity of 1-methoxy-2-propanol = (Peak area of ​​1-methoxy-2-propanol in the product separated in step b) / (Area of ​​all peaks) × 100%

[0056] 2-Methoxy-1-propanol yield = (Mass of 2-methoxy-1-propanol in the product separated in step b) / (Mass of 2-methoxy-1-propanol in the alcohol ether wastewater) × 100%

[0057] Purity of 2-methoxy-1-propanol = (Peak area of ​​2-methoxy-1-propanol in the product separated in step b) / (Area of ​​all peaks) × 100%

[0058] Example 1

[0059] The alcohol and ether wastewater from the industrial propylene oxide plant contains 2.5% propylene glycol, 4.6% 1-methoxy-2-propanol, and 2.1% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, inorganic salts, and other impurities.

[0060] Following the process shown in Figure 1 (tower A), under atmospheric pressure and at 20°C, alcohol ether wastewater and hexafluoroisopropanol (solubility in water: 100g / 100g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.3. The theoretical number of plates in this extraction tower is 12. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water and inorganic salts, while the heavy phase mainly contains extractant, propylene glycol, propylene glycol ether, and small amounts of dipropylene glycol and tripropylene glycol.

[0061] The heavy phase obtained after extraction was introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant component, propylene glycol, and propylene glycol ether component were obtained from outlets 6 and 7, respectively. The extractant component was returned to column A for continued use as an extractant. The propylene glycol and propylene glycol ether components were further distilled to obtain 1-methoxy-2-propanol, 2-methoxy-1-propanol, and propylene glycol sequentially. The yields and purities of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0062] Example 2

[0063] The alcohol and ether wastewater from the industrial propylene oxide plant contains 2.5% propylene glycol, 4.6% 1-methoxy-2-propanol, and 2.1% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, inorganic salts, and other impurities.

[0064] Following the process shown in Figure 1 (tower A), under atmospheric pressure and at 30°C, alcohol ether wastewater and 2,2,3,3-tetrafluoropropanol (solubility in water > 1 g / 100 g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.5. The theoretical number of plates in this extraction tower is 15. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water and inorganic salts, while the heavy phase mainly contains extractant, propylene glycol, propylene glycol ether, and small amounts of dipropylene glycol and tripropylene glycol.

[0065] The heavy phase obtained after extraction was introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant, propylene glycol ether component, and propylene glycol component were obtained from outlets 6 and 7, respectively. The extractant and propylene glycol ether component were further distilled to obtain the extractant, 1-methoxy-2-propanol, and 2-methoxy-1-propanol sequentially. The extractant component was returned to column A for continued use as an extractant. The yields and purity of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0066] Example 3

[0067] The alcohol and ether wastewater from the industrial propylene oxide plant contains 2.5% propylene glycol, 4.6% 1-methoxy-2-propanol, and 2.1% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, inorganic salts, and other impurities.

[0068] Following the process shown in Figure 1 (tower A), under conditions of 40℃ and 0.5MPa, alcohol ether wastewater and perfluorotert-butanol (solubility in water > 1g / 100g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.2. The theoretical number of plates in this extraction tower is 8. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water and inorganic salts, while the heavy phase mainly contains extractant, propylene glycol, propylene glycol ether, and small amounts of dipropylene glycol and tripropylene glycol.

[0069] The heavy phase obtained after extraction was then introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant component, propylene glycol, and propylene glycol ether component were obtained from outlets 6 and 7, respectively. The extractant component was returned to column A for continued use as an extractant. The propylene glycol and propylene glycol ether components were further distilled to obtain 1-methoxy-2-propanol, 2-methoxy-1-propanol, and propylene glycol sequentially. The yields and purity of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0070] Example 4

[0071] The wastewater from the industrial propylene oxide plant contains 5.1% propylene glycol, 18.4% 1-methoxy-2-propanol, and 11.6% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, salts, and other impurities.

[0072] Following the process shown in Figure 1 (tower A), under conditions of 40℃ and 0.5MPa, alcohol ether wastewater and hexafluoroisopropanol (solubility in water: 100g / 100g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.5. The theoretical number of plates in this extraction tower is 20. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water and a small amount of salt, while the heavy phase mainly contains extractant, propylene glycol, propylene glycol ether, and small amounts of dipropylene glycol and tripropylene glycol.

[0073] The heavy phase obtained after extraction was introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant component, propylene glycol, and propylene glycol ether component were obtained from outlets 6 and 7, respectively. The extractant component was returned to column A for continued use as an extractant. The propylene glycol and propylene glycol ether components were further distilled to obtain 1-methoxy-2-propanol, 2-methoxy-1-propanol, and propylene glycol sequentially. The yields and purities of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0074] Example 5

[0075] The wastewater from the industrial propylene oxide plant contains 15.6% propylene glycol, 3.1% 1-methoxy-2-propanol, and 1.2% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, salts, and other impurities.

[0076] Following the process shown in Figure 1 (tower A), under atmospheric pressure and at 40°C, alcohol ether wastewater and perfluorotert-butanol (solubility in water > 1 g / 100 g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.2. The theoretical number of plates in this extraction tower is 22. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water and a small amount of salt, while the heavy phase mainly contains extractant, propylene glycol, propylene glycol ether, and small amounts of dipropylene glycol and tripropylene glycol.

[0077] The heavy phase obtained after extraction was then introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant component, propylene glycol, and propylene glycol ether component were obtained from outlets 6 and 7, respectively. The extractant component was returned to column A for continued use as an extractant. The propylene glycol and propylene glycol ether components were further distilled to obtain 1-methoxy-2-propanol, 2-methoxy-1-propanol, and propylene glycol sequentially. The yields and purity of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0078] Example 6

[0079] The wastewater from the industrial propylene oxide plant contains 15.6% propylene glycol, 3.1% 1-methoxy-2-propanol, and 1.2% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, salts, and other impurities.

[0080] Following the process shown in Figure 1 (tower A), under conditions of 60℃ and 0.5MPa, alcohol ether wastewater and 2,2,3,3-tetrafluoropropanol (solubility in water > 1g / 100g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.3. The theoretical number of plates in this extraction tower is 18. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water and inorganic salts, while the heavy phase mainly contains extractant, propylene glycol, propylene glycol ether, and small amounts of dipropylene glycol and tripropylene glycol.

[0081] The heavy phase obtained after extraction was introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant, propylene glycol ether component, and propylene glycol component were obtained from outlets 6 and 7, respectively. The extractant and propylene glycol ether component were further distilled to obtain the extractant, 1-methoxy-2-propanol, and 2-methoxy-1-propanol sequentially. The extractant component was returned to column A for continued use as an extractant. The yields and purity of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0082] Example 7

[0083] The alcohol and ether wastewater from the industrial propylene oxide plant was taken, in which the mass fraction of 1-methoxy-2-propanol was 14.3%, the mass fraction of 2-methoxy-1-propanol was 5.5%, and the remainder contained small amounts of propylene glycol, dipropylene glycol, tripropylene glycol, salts and other impurities.

[0084] Following the process shown in Figure 1 (tower A), under atmospheric pressure and at 30°C, alcohol ether wastewater and hexafluoroisopropanol (solubility in water 100g / 100g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.4. The theoretical number of plates in this extraction tower is 15. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water and a small amount of salt, while the heavy phase mainly contains extractant, propylene glycol ether, and small amounts of propylene glycol, dipropylene glycol, and tripropylene glycol.

[0085] The heavy phase obtained after extraction was introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant component and propylene glycol ether component were obtained from outlets 6 and 7, respectively. The extractant component was returned to column A for continued use as an extractant. The propylene glycol ether component was further distilled to obtain 1-methoxy-2-propanol and 2-methoxy-1-propanol. The yields and purity of 1-methoxy-2-propanol and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0086] Example 8

[0087] The alcohol and ether wastewater from the industrial propylene oxide plant contains 2.5% propylene glycol, 4.6% 1-methoxy-2-propanol, and 2.1% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, inorganic salts, and other impurities.

[0088] Following the process shown in Figure 1 (tower A), under atmospheric pressure and at 20°C, alcohol ether wastewater and 2,3-dichloro-1-propanol (solubility in water: 12 g / 100 g) are introduced into the extraction tower through inlets 1 and 2 respectively for countercurrent contact extraction. The mass flow ratio of alcohol ether wastewater to extractant is 1:0.3. The theoretical number of plates in this extraction tower is 12. Light and heavy phases are obtained at outlets 3 and 4. The light phase mainly contains water, inorganic salts, and a small amount of extractant, while the heavy phase mainly contains extractant, propylene glycol, propylene glycol ether, water, and small amounts of dipropylene glycol and tripropylene glycol.

[0089] The heavy phase obtained after extraction was introduced into a distillation column through inlet 5 for distillation separation, as shown in column B of Figure 2. The extractant component, propylene glycol, and propylene glycol ether component were obtained from outlets 6 and 7, respectively. The extractant component was returned to column A for continued use as an extractant. The propylene glycol and propylene glycol ether components were further distilled to obtain 1-methoxy-2-propanol, 2-methoxy-1-propanol, and propylene glycol sequentially. The yields and purities of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0090] Comparative Example 1

[0091] The alcohol and ether wastewater from the industrial propylene oxide plant contains 2.5% propylene glycol, 4.6% 1-methoxy-2-propanol, and 2.1% 2-methoxy-1-propanol. The remainder contains small amounts of dipropylene glycol, tripropylene glycol, inorganic salts, and other impurities.

[0092] The alcohol ether wastewater was first concentrated, and the resulting light phase was subjected to azeotropic distillation in a dehydration tower to remove water, yielding a propylene glycol ether component. This propylene glycol ether component was then distilled to obtain 1-methoxy-2-propanol and 2-methoxy-1-propanol. The heavy phase of the concentrated alcohol ether wastewater was then concentrated in propylene glycol, yielding wastewater and a concentrated propylene glycol component. This concentrated propylene glycol component was then distilled to recover propylene glycol. The yields and purities of propylene glycol, 1-methoxy-2-propanol, and 2-methoxy-1-propanol were analyzed, and the results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As can be seen from the results of Examples 1-8 and Comparative Example 1, the method of the present invention for separating alcohol ether wastewater has a simple process flow, requires no special equipment, has a simple extractant composition, is easy to separate from other products in the raw materials, and has high yields and purity of propylene glycol and propylene glycol ether. The aqueous phase and extractant phase after separation can be reused, so the material utilization rate is high and it is suitable for large-scale industrial production applications.

Claims

1. A method for recovering propylene glycol and propylene glycol methyl ether from alcohol ether wastewater, characterized in that, The method includes: step a: mixing alcohol ether wastewater with an extractant and then extracting and separating the mixture to obtain a heavy phase and a light phase; and step b: separating the heavy phase obtained in step a to obtain a product containing propylene glycol and / or propylene glycol methyl ether; wherein the extractant includes a haloalcohol.

2. The method according to claim 1, characterized in that, The alcohol ether wastewater is alcohol ether wastewater generated from the propylene oxide unit or alcohol ether wastewater generated in the experiment.

3. The method according to claim 1, characterized in that, The mass fraction of alcohols and / or ethers in the alcohol-ether wastewater shall not be less than 0.1%, preferably not less than 1%.

4. The method according to claim 1, characterized in that, The alcohols are one or more of propylene glycol, ethylene glycol, dipropylene glycol, tripropylene glycol, and glycerol; the ethers are one or more of 1-methoxy-2-propanol and 2-methoxy-1-propanol.

5. The method according to claim 1, characterized in that, The solubility of the haloalcohol in water is not less than 1 g / 100 g.

6. The method according to claim 1, characterized in that, The haloalcohol has m carbon atoms, where m is a positive integer from 1 to 12, preferably 2 to 8, and more preferably 3 to 6. In the haloalcohol, the halogen element, hydroxyl group, and hydrogen are bonded to the carbon atoms. The halogen element is one or more of fluorine, chlorine, bromine, and iodine, and its number does not exceed 2m+1. The number of hydroxyl groups does not exceed 5, preferably not more than 3, and more preferably 1.

7. The method according to claim 6, characterized in that, The halogen element of the haloalcohol is fluorine.

8. The method according to claim 1 or 7, characterized in that, The haloalcohol is selected from 2-fluoroethanol, trifluoroethanol, 1-chloro-2-propanol, 3-chloro-1-propanol, 2-chloro-1-propanol, 1,3-dichloropropanol, 2,3-dichloro-1-propanol, bromopropanol, 2,2,3,3-tetrafluoropropanol, 1H,1H-pentafluoropropanol, 3-fluoropropanol, hexafluoroisopropanol, 1,1,1,3,3,3-hexafluoro-2-deuterated propanol, and 2-allyl hexafluoroisopropanol. 1,3-Difluoro-2-propanol, hexafluoro-2-methylisopropanol, perfluorotert-butanol, 1-chloro-3-fluoro-2-propanol, 3-bromo-1,1,1-trifluoro-2-propanol, 2-trifluoromethyl-2-propanol, 2,2-bis(trifluoromethyl)propanol, 2,2-difluoropropanol, 3-bromo-trifluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propanol, 3-(3-trifluoro-2-propanol) 2-(4-fluorophenyl)-2-propanol, 2-[3,5-(bis(trifluoromethyl)phenyl)-2-propanol), 1,3-bis(1,1,1,3,3,3-hexafluoro-2-propanol)benzene, 3-perfluorooctylpropanol, 3-(perfluorohexyl)propanol, (R)-(+)-1-chloro-3-(4-fluorophenoxy)-2-propanol, 1-(4-fluoropropoxy)-2-propanol, 1 One or more of the following: 1,1-trifluoro-2-propanol, 3,3,3-trifluoro-1-propanol, 2-vinylhexafluoroisopropanol, 2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoro-2-propanol, hexafluoro-2-(p-tolyl)isopropanol, 1-(4-trifluoromethylphenyl)-1-propanol, 3-perfluorobutyl-2-propanol, and 3-(perfluoro-7-methylhexyl)-2-iodopropanol.

9. The method according to claim 8, characterized in that, The haloalcohol is selected from 1-chloro-2-propanol, 3-chloro-1-propanol, 2-chloro-1-propanol, 1,3-dichloropropanol, 2,3-dichloro-1-propanol, bromopropanol, 2,2,3,3-tetrafluoropropanol, 1H,1H-pentafluoropropanol, 3-fluoropropanol, hexafluoroisopropanol, 1,1,1,3,3,3-hexafluoro-2-deuterated propanol, 2-allyl hexafluoroisopropanol, 1,3-difluoro-2-propanol, hexafluoro-2- One or more of the following: methyl isopropanol, perfluorotert-butanol, 1-chloro-3-fluoro-2-propanol, 2-trifluoromethyl-2-propanol, 2,2-bis(trifluoromethyl)propanol, 2,2-difluoropropanol, 3-bromo-trifluoro-2-propanol, 1-(4-fluoropropoxy)-2-propanol, 1,1,1-trifluoro-2-propanol, 3,3,3-trifluoro-1-propanol, 2-vinylhexafluoroisopropanol, and 3-perfluorobutyl-2-propanol.

10. The method according to claim 9, characterized in that, The haloalcohol is selected from one or more of the following: 2,2,3,3-tetrafluoropropanol, 1H,1H-pentafluoropropanol, 3-fluoropropanol, hexafluoroisopropanol, 2-allylhexafluoroisopropanol, 1,3-difluoro-2-propanol, hexafluoro-2-methylisopropanol, perfluorotert-butanol, 2-trifluoromethyl-2-propanol, 2,2-bis(trifluoromethyl)propanol, 2,2-difluoropropanol, 1-(4-fluoropropoxy)-2-propanol, 1,1,1-trifluoro-2-propanol, 3,3,3-trifluoro-1-propanol, and 2-vinylhexafluoroisopropanol.

11. The method according to claim 1, characterized in that, The mixing described in step a can be performed in an intermittent or continuous manner.

12. The method according to claim 1, characterized in that, In step a, the extraction and separation are carried out by standing, settling, centrifugation, and decantation.

13. The method according to claim 1, characterized in that, In step a, the weight ratio of alcohol ether wastewater to extractant is 1:(0.01-10), preferably 1:(0.05-5), further preferably 1:(0.1-1), more preferably 1:(0.15-0.8), and most preferably 1:(0.2-0.5).

14. The method according to claim 1, characterized in that, In step a, the mixing is carried out at 5–80°C and atmospheric pressure to 2 MPa, preferably at 20–60°C and atmospheric pressure to 0.5 MPa.

15. The method according to claim 1, characterized in that, The separation described in step b is distillation or rectification, and can be carried out continuously or intermittently. The separation is a single separation unit or a combination of multiple separation units.

16. The method according to claim 1, characterized in that, It also includes using part or all of the extractant obtained from the heavy phase in step b to repeat the mixing and separation process in step a.

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