A method for purifying beta-phenylethanol

Abstract

This invention provides a method for purifying β-phenylethanol. The feed stream 1 is the bottom liquid from the styrene separation reaction of α-phenylethanol in the ethylene-phenyl co-oxidation process for producing propylene oxide. The method includes: receiving a solution stream 2 of thiourea compounds at the upper part of an extraction tower; receiving an extractant stream 3 in the middle part of the extraction tower; receiving the feed stream 1 at the lower part of the extraction tower; obtaining an oil phase stream 4 after impurity removal and extraction in the extraction tower; collecting waste liquid at the bottom of the extraction tower; passing the oil phase stream 4 into a crystallizer for crystallization and purification to obtain a product stream 5; the solution stream 2 of thiourea compounds is a thiourea compound, which can effectively remove aldehydes and ketones. This invention can obtain a high-purity β-phenylethanol product with acceptable aroma.

Description

Technical Field

[0001] This invention belongs to the field of chemical process and relates to a method for purifying β-phenylethanol. Specifically, it relates to a method for extracting β-phenylethanol from the bottom liquid of the column after the α-phenylethanol dehydration reaction to separate styrene in the ethylbenzene co-oxidation process for producing propylene oxide. Background Technology

[0002] β-Phenylacetyl alcohol is a liquid with a rose aroma, naturally found in aromatic oils such as neroli oil, rose oil, and geranium oil. Its gentle, pleasant rose scent makes it widely used in the fragrance and flavor industry, as well as in the daily chemical industry. Currently, the global production capacity of β-phenylethanol is approximately 25,000 tons per year, second only to vanillin in terms of usage.

[0003] Currently, the main production processes for β-phenylethanol are chemical methods, including Friedel-Crafts alkylation, epoxidation hydrogenation, and biosynthesis. Friedel-Crafts alkylation produces numerous byproducts, affecting the aroma of β-phenylethanol, and the acid catalyst is not environmentally friendly. The epoxidation hydrogenation of styrene to produce β-phenylethanol involves hazardous processes; the epoxidation unit has a low single-pass yield and high material consumption, leading to high overall costs and impacting the product's economic viability. Biosynthesis of β-phenylethanol offers advantages such as mild reaction conditions, a wide range of raw material sources, and food-grade β-phenylethanol; however, the fermentation process is inefficient, requires strain selection, and cannot be used for continuous production.

[0004] In the ethylbenzene peroxidation process for producing propylene oxide, the product obtained from the reaction of ethylbenzene hydrogen peroxide with propylene, after propylene recovery, is separated from heavy components such as ethylbenzene and α-phenylethanol by a propylene oxide separation tower. α-Phenylene is dehydrated to produce styrene, which is then separated from heavy components such as β-phenylethanol, 1-phenyl-2-propanol, ethylphenol, acetal, and oligomers by a styrene separation tower. β-Phenylene constitutes a high proportion of these heavy components, and its incineration would result in significant resource waste; therefore, β-phenylethanol has high recovery value.

[0005] CN117088756A uses a scraper to separate the polymer, and then uses aldehydes to react with phenolic impurities to remove phenols. However, this process introduces new aldehyde impurities, affecting the odor of β-phenylethanol, making it unsuitable for applications with high odor requirements. CN116239432A uses heavy oil cracking to recover styrene during the phenylethanol separation process, but there are risks such as heavy fraction tar clogging the trays and heat exchangers. Currently, the recovery of β-phenylethanol from the bottom liquid of the tower after the α-phenylethanol dehydration reaction to separate styrene in the ethylene co-oxidation process for propylene oxide production is difficult, and obtaining high-purity, odor-compliant β-phenylethanol efficiently is even more challenging. Summary of the Invention

[0006] The purpose of this invention is to provide a method for purifying β-phenylethanol, which extracts β-phenylethanol from the bottom liquid of the column after the α-phenylethanol dehydration reaction to separate styrene in the ethylbenzene co-oxidation process for producing propylene oxide, thereby solving the problems of low purity and substandard aroma of β-phenylethanol products in existing methods.

[0007] To achieve one aspect of the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A method for purifying β-phenylethanol, wherein feed stream 1 is the bottom liquid from the dehydration reaction of α-phenylethanol to styrene in the ethylbenzene co-oxidation process for producing propylene oxide, the method comprising:

[0009] A solution stream 2 of thiourea compound is received at the upper part of the extraction tower, an extractant stream 3 is received in the middle part of the extraction tower, and a raw material stream 1 is received at the lower part of the extraction tower. The raw material stream 1 is purified and extracted in the extraction tower to obtain an oil phase stream 4. Waste liquid is collected at the bottom of the extraction tower. The oil phase stream 4 is passed into a crystallizer and purified by crystallization to obtain a product stream 5.

[0010] In this context, the solution stream 2 of the thiourea compound is a solution of the thiourea compound.

[0011] In some embodiments, the thiourea compound is one or more of thiourea, alkylthiourea, aromatic thiourea, and aminothiourea. Preferably, the thiourea compound is thiourea or alkylthiourea, and more preferably, one or more of thiourea, tetramethylthiourea, 1,3-dimethylthiourea, ethylthiourea, and diethylthiourea.

[0012] In some embodiments, the mass fraction of thiourea compound in the solution stream 2 is 2wt% to 70wt%, and the flow rate-to-mass ratio of the solution stream 2 to the raw material stream 1 is 1:1 to 1:10, preferably 1:5 to 1:8.

[0013] Preferably, the molar ratio of the thiourea compound in the solution stream 2 to the aldehyde and ketone in the raw material stream 1 is 1:1 to 8:1, more preferably 1:1 to 3:1.

[0014] In some embodiments, the solvent in the solution stream 2 of the thiourea compound is water or an organic solvent, or the extractant in the extractant stream 3 is used as the solvent, wherein the organic solvent is one or more of dichloromethane, dichloroethane, toluene, and ethylbenzene; preferably, the extractant is used as the solvent.

[0015] In some embodiments, the extractant is one or more of dichloromethane, dichloroethane, toluene, and ethylbenzene; preferably, the mass ratio of the extractant stream 3 to the raw material stream 1 is 2:1 to 1:1, more preferably 1.5:1 to 1.1:1.

[0016] In some embodiments, the extraction tower is a rotating disc extraction tower.

[0017] In some embodiments, the number of rotating discs in the rotating disc extraction tower is 15 to 40, preferably 20 to 35.

[0018] In some embodiments, the total amount of the thiourea compound solution stream 2 is controlled so that the aldehyde and ketone content in the oil phase stream 4 is between 0.1 ppm and 100 ppm, preferably between 1 ppm and 30 ppm.

[0019] In some embodiments, the crystallizer is a dynamic crystallizer.

[0020] In some embodiments, the final temperature of the cooling process in the crystallization curve of the crystallizer is -40°C to -45°C.

[0021] In some embodiments, the refrigerant temperature of the crystallizer is -60°C to 7°C, and the heat medium temperature is 10°C to 25°C.

[0022] In some embodiments, the impurities contained in the raw material stream 1 are one or more of alcohols, aldehydes, ketones, phenols, and oligomers. Preferably, the alcohols include one or more of α-phenylethanol, 1-phenyl-2-propanol, and 2-phenyl-1-propanol; the aldehydes include one or more of benzaldehyde, phenylacetaldehyde, acetal, and polyacetal; the phenols include one or more of phenol, ethylphenol, 2,4-xylenol, and 2,6-xylenol, wherein ethylphenol includes one or more of o-ethylphenol, p-ethylphenol, and m-ethylphenol; and the oligomers include polystyrene oligomers.

[0023] Preferably, the β-phenylethanol content in the raw material stream 1 is 10wt% to 70wt%, more preferably 20wt% to 60wt%.

[0024] Preferably, the aldehyde content in the raw material stream 1 is 0.1wt% to 3wt%, more preferably 0.5wt% to 1wt%.

[0025] Preferably, the ketone content in the raw material stream 1 is 0.1wt% to 3wt%, more preferably 0.5wt% to 1wt%.

[0026] Preferably, the phenol content in the raw material stream 1 is 0.1wt% to 15wt%, more preferably 0.5wt% to 10wt%.

[0027] Preferably, the 1-phenyl-2-propanol content in the raw material stream 1 is 0.1 wt% to 2 wt%, more preferably 0.5 wt% to 1 wt%.

[0028] In some embodiments, the β-phenylethanol in product stream 5 has a purity ≥99.9%, an aldehyde content ≤0.01ppm, a ketone content ≤1ppm, a phenol content ≤1ppm, a 1-phenyl-2-propanol content ≤1ppm, and an ethylphenol content ≤1ppm.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The present invention uses an extraction tower and a crystallizer to obtain β-phenylethanol product. By combining impurity removal, extraction and crystallization, impurities such as phenols, aldehydes and ketones, acetals and oligomers in the bottom liquid of the tower after the separation of styrene from the dehydration reaction of α-phenylethanol can be effectively removed, and a high-purity β-phenylethanol product with qualified aroma can be obtained, which can effectively reduce production costs.

[0031] (2) β-Phenylacetyl alcohol has a mild, lasting rose scent and is a colorless liquid. In the process of producing propylene oxide by ethylbenzene co-oxidation, the bottom liquid of the tower after the dehydration reaction of α-phenylethanol to separate styrene contains aldehydes such as benzaldehyde and phenylacetaldehyde. As is well known, aldehydes are chemically active and easily oxidize in the air to form acids, which affect the odor and color of the product. Moreover, aldehydes have their own unique odor and a very low odor threshold. Even if there is very little residue in the system, it will affect the odor of β-phenylethanol. Therefore, the removal of aldehyde compounds is particularly important. This invention utilizes thiourea compounds to remove aldehydes and ketones at the same time. Thiourea compounds react with aldehyde or ketone groups to form stable thiourea compounds and the reactants formed by aldehydes and ketones. After extraction with an extractant, the reactants formed by thiourea compounds and aldehydes and ketones are discharged from the extraction tower with the waste liquid, thereby removing aldehydes and ketones at the same time.

[0032] (3) The present invention can discharge oligomers and complexes generated during the removal of aldehydes and ketones through the extraction tower, thus avoiding problems such as tower blockage. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a process for purifying β-phenylethanol according to one embodiment of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] In one aspect, the present invention provides a method for purifying β-phenylethanol, the method being used to separate and purify β-phenylethanol from the bottom liquid of the column after the styrene separation reaction of α-phenylethanol in the ethylbenzene co-oxidation process for producing propylene oxide, the method comprising:

[0036] A solution stream 2 of thiourea compound is received at the upper part of the extraction tower, an extractant stream 3 is received in the middle part of the extraction tower, and a raw material stream 1 is received at the lower part of the extraction tower. The raw material stream 1 is purified and extracted in the extraction tower to obtain an oil phase stream 4. Waste liquid is collected at the bottom of the extraction tower. The oil phase stream 4 is passed into a crystallizer and purified by crystallization to obtain a product stream 5.

[0037] In this context, the solution stream 2 of the thiourea compound is a solution of the thiourea compound.

[0038] In this invention, the position of the outlet of the oil phase stream 4 is not particularly limited, but it is preferably set at a position higher than the receiving port of the raw material stream 1, for example, the outlet of the oil phase stream 4 is in the middle or upper part of the extraction tower.

[0039] In their research, the inventors discovered that thiourea compounds can react with aldehyde and ketone groups to form stable thiourea compounds and aldehyde-ketone reactants. Thiourea compounds contain a sulfur atom and a urea group. The sulfur atom has strong nucleophilicity and undergoes nucleophilic addition reactions with aldehyde or ketone groups. Additionally, the urea group also reacts with aldehyde or ketone groups to form urea derivatives. The reaction mechanism is illustrated below using thiourea as an example.

[0040]

[0041] The reaction product formed by the thiourea compound and aldehydes / ketones is extracted with an extractant to remove aldehyde and ketone impurities. In this invention, the content of thiourea compound in the thiourea compound solution stream 2 is generally in excess of the aldehyde and ketone content in the feed stream 1 to completely remove the aldehydes and ketones from the feed stream 1; from the perspective of reducing the consumption of thiourea compound solution stream 2, a slight excess is preferred. For example, the molar ratio of thiourea compound in the thiourea compound solution stream 2 to the aldehyde and ketone content in the feed stream 1 is 1:1 to 8:1, preferably 1:1 to 3:1. To make the content of thiourea compound in the thiourea compound solution stream 2 in excess of the aldehyde and ketone content in the feed stream 1, for example, this can be achieved by adjusting the flow rate-to-mass ratio of the feed stream 1 and the thiourea compound solution stream 2 and / or the mass fraction of thiourea compound in the thiourea compound solution stream 2. Excess thiourea is partially discharged with the waste liquid in the extraction tower, while the rest can be removed in the crystallizer. Because the melting point of thiourea compounds differs significantly from that of β-phenylethanol, the unreacted thiourea compounds can be easily removed in the crystallizer. Typically, the content of thiourea compounds in crystallized β-phenylethanol products can be so low that it is difficult to detect by chromatographic analysis.

[0042] In some embodiments, the thiourea compound is a thiourea compound commonly used in the art, such as thiourea, alkylthiourea, aromatic thiourea, aminothiourea, etc., preferably one or more of thiourea and alkylthiourea, more preferably one or more of thiourea, tetramethylthiourea, 1,3-dimethylthiourea, ethylthiourea, and diethylthiourea.

[0043] In some embodiments, the mass fraction of thiourea compound in the solution stream 2 is 2wt% to 70wt%, and the flow rate-to-mass ratio of the solution stream 2 to the raw material stream 1 is 1:1 to 1:10, preferably 1:5 to 1:8.

[0044] In one embodiment, the solvent in the solution stream 2 of the thiourea compound is water or an organic solvent, or the extractant in the extractant stream 3 is used as the solvent, wherein the organic solvent is one or more of dichloromethane, dichloroethane, toluene, and ethylbenzene; preferably, the extractant is used as the solvent. To reduce the amount of extractant used and decrease separation energy consumption, the extractant is preferably used as the solvent.

[0045] In some embodiments, the extractant is one or more of dichloromethane, dichloroethane, toluene, and ethylbenzene; preferably, the mass ratio of the extractant stream 3 to the raw material stream 1 is 2:1 to 1:1, more preferably 1.5:1 to 1.1:1.

[0046] In this invention, the raw material stream 1 comes from the bottom liquid of the tower after the α-phenylethanol dehydration reaction to separate styrene in the ethylene-phenyl co-oxidation process for producing propylene oxide. This invention does not have any special limitations on it, and any bottom liquid produced by this process is applicable to the method of this invention.

[0047] In some embodiments, the extraction tower is any suitable type of extraction tower, such as a rotating disc extraction tower.

[0048] In some embodiments, the crystallizer is any suitable type of crystallizer, such as a dynamic crystallizer.

[0049] In this invention, the mass fraction of β-phenylethanol in the raw material stream 1 is 10 wt% to 70 wt%, for example, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, or 70 wt%. Specifically, the impurities contained in the raw material stream 1 are one or more of alcohols, aldehydes, ketones, phenols, and oligomers. The alcohols are mainly α-phenylethanol, 1-phenyl-2-propanol, 2-phenyl-1-propanol, etc.; the aldehydes are mainly benzaldehyde, phenylacetaldehyde, acetal, polyacetal, etc., and specifically, the mass fraction of aldehydes is 0.1 wt% to 3 wt%, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%; the mass fraction of ketones is 0.1 wt% to 3 wt%, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%; the phenols are mainly phenol, ethylphenol, 2,4-xylenol, 2,6-xylenol, etc., and ethylphenol includes, for example, o-ethylphenol, p-ethylphenol, m-ethylphenol, and specifically, the mass fraction of phenols is 0.1 wt%. The oligomers are wt% to 15 wt%, for example, 0.1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, and 15 wt%; particularly, the ethylphenol is 2 wt% to 15 wt%, for example, 2 wt%, 5 wt%, 8 wt%, 12 wt%, and 15 wt%. Specifically, the 1-phenyl-2-propanol is 0.1 wt% to 2 wt%, for example, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, and 2 wt%. The oligomers include, for example, oligostyrene.

[0050] In one embodiment, the feed stream 1, after aldehyde and ketone removal and extraction in the extraction tower, yields an oil phase stream 4. The oil phase stream 4 enters a crystallizer for further purification, removing alcohol and phenol impurities with boiling points close to β-phenylethanol. For example, regarding the impurity o-ethylphenol, research has shown that in the binary eutectic system of o-ethylphenol and β-phenylethanol, the lowest eutectic point composition is around 0.6, with a eutectic point of approximately -40 to -45°C. This means that when the molar fraction of o-ethylphenol in the mixture is below 0.6, a solid phase with β-phenylethanol as the main component can be obtained through crystallization separation. Conversely, if the molar fraction of o-ethylphenol in the mixture is above 0.6, a solid phase with o-ethylphenol as the main component can be obtained through crystallization separation. In this invention, the molar fraction of β-phenylethanol in the oil phase stream 4 is typically >0.8. By setting a crystallization curve based on the lowest eutectic point composition and corresponding eutectic point of o-ethylphenol and β-phenylethanol, high-purity β-phenylethanol can be obtained.

[0051] In some examples of this invention, the oil phase stream 4 enters the crystallizer and undergoes purification through four stages: crystallization and mother liquor discharge, sweating (partial melting), melting (complete melting), and purified product discharge. Crystallization and mother liquor discharge process: The refrigerant is set to gradient cooling, and the melt forms crystal nuclei on the inner wall of the crystallization tube. As the temperature gradually decreases, crystallization occurs slowly. After the crystallization process is complete, the mother liquor with lower purity is discharged. Sweating: To further purify the crystals, the heat medium on the outer wall of the tube is gradually heated to a set value (slightly below the product's melting point). During this process, impurities adhering to the crystal surface and impurities trapped between crystals gradually flow out through the gaps between the crystal layers. The sweating process further improves the purity of the crystals, and at this point, the inner wall of the crystallizer contains high-purity crystals. Melting: The temperature of the heat medium is further increased to a set value (slightly above the product's melting point), causing the crystallized product to completely melt. Finally, the purified product is discharged and collected.

[0052] In one embodiment, in the crystallization curve of the crystallizer (e.g., a dynamic crystallizer), the endpoint temperature of the cooling process is -40°C to -45°C. In this invention, the endpoint temperature is the lowest temperature of the cooling process in the crystallization curve, and also the lowest temperature of the entire crystallization curve.

[0053] In one embodiment, the refrigerant temperature is -60°C to 7°C; the heat medium temperature of the crystallizer is 10°C to 25°C. Furthermore, in this invention, the crystallization time is not particularly limited and can be adjusted as needed.

[0054] The following embodiments further illustrate the technical solutions provided by the present invention, but the present invention is not limited to the listed embodiments, and also includes any other known modifications within the scope of the present invention.

[0055] Analytical instrument: Anglient 8890A gas chromatograph (flame ionization detector, nitrogen as carrier gas) was used for analysis, employing an HP-INNOWAX capillary column (polyethylene glycol, 60 m × 0.25 mm × 0.25 µm) and a flame ionization detector (FID). The injector and detector temperatures were both 250 °C; the column temperature was programmed: initial temperature 80 °C, held for 2 minutes, then increased to 240 °C at 1 °C / min, and held for 7 minutes. Column pressure was 8.5868 psi, and the flow rate was 1.50 mL / min. Injection volume: 0.2 µL. Conversion and selectivity were calculated using hexylbenzene as an internal standard.

[0056] Aroma evaluation: conducted in accordance with GB / T 14454.2-2008; two professional perfumers were selected, and the sample was dropped onto the evaluation paper. The professional perfumers evaluated and recorded the aroma attributes, intensity, top notes, middle notes, and base notes.

[0057] Raw material sources: Stream 1 is the bottom liquid from the styrene separation tower after the dehydration reaction of α-phenylethanol, which comes from the Wanhua Chemical ethylbenzene co-oxidation to propylene oxide and styrene co-production unit; other reagents are all purchased from Maclean's reagents, which are commercially available.

[0058] Equipment source: The rotary extraction tower is from Shanghai Sulzer Engineering Machinery Manufacturing Co., Ltd., model ECR60;

[0059] The dynamic crystallizer, sourced from Shanghai Donggeng Chemical Technology Co., Ltd., has a diameter of DN500 and a height of 3m. The crystallization curves for the following examples are shown below:

[0060]

[0061] The process flow diagrams of the following embodiments are shown below. Figure 1 .

[0062] Example 1

[0063] A solution stream 2 of thiourea compounds is received at the top of the rotary extractor column, an extractant stream 3 is received in the middle of the column, and a feed stream 1 is received at the bottom. The rotary extractor column has 15 trays and rotates at 200 rpm. Feed stream 1 contains 40 wt% β-phenylethanol, 1 wt% total aldehydes and ketones, 10 wt% phenols, and 0.5 wt% 1-phenyl-2-propanol, with other components mainly consisting of other alcohols and polymers. The solution stream 2 of thiourea compounds is a dichloromethane solution of thiourea (concentration 12 wt%). The flow rate of feed stream 1 is 1 t / h, and the flow rate of the solution stream 2 is 200 kg / h (the molar ratio of thiourea compounds in solution stream 2 to the aldehydes and ketones in feed stream 1 is approximately 3.8:1). The extractant stream 3 is dichloromethane. Methane was used as the extractant at a flow rate of 2 t / h. After impurity removal and extraction, oil stream 4 was obtained. Oil stream 4 entered a dynamic crystallizer for crystallization. The refrigerant temperature was -42℃ and the heating medium temperature was 15℃. The flow rates of the refrigerant and heating medium were adjusted to control the dynamic crystallization time to 6 h. After crystallization and purification, product stream 5 was obtained. The purity of β-phenylethanol in product stream 5 was 99.98%, and the product yield was about 75%. The content of aldehydes and ketones was less than 1 ppm, the content of phenols was less than 1 ppm, and the content of 1-phenyl-2-propanol was less than 1 ppm. The product odor was evaluated as a soft and lasting rose fragrance.

[0064]

[0065] Example 2

[0066] A solution stream 2 of thiourea compounds is received at the top of the rotary extractor column, an extractant stream 3 is received in the middle of the column, and a feed stream 1 is received at the bottom. The rotary extractor column has 35 trays and rotates at 200 rpm. Feed stream 1 contains 60 wt% β-phenylethanol, 3 wt% total aldehydes and ketones, 15 wt% phenols, and 2 wt% 1-phenyl-2-propanol, with other components mainly consisting of other alcohols and polymers. The solution stream 2 of thiourea compounds is an aqueous solution of 1,3-dimethylthiourea (concentration 15 wt%). The flow rate of feed stream 1 is 1 t / h, and the flow rate of thiourea compound solution stream 2 is 500 kg / h (the molar ratio of thiourea compounds in solution stream 2 to aldehydes and ketones in feed stream 1 is approximately 2.9:1). Toluene is used as the extractant in extractant stream 3, with a flow rate of 1.5 kg / h. After impurity removal and extraction, oil phase stream 4 is obtained. Oil phase stream 4 enters a dynamic crystallizer for crystallization. The refrigerant temperature is -60℃ and the heating medium temperature is 10℃. The dynamic crystallization time is controlled by adjusting the flow rate of the refrigerant and heating medium. After crystallization and purification, product stream 5 is obtained. The purity of β-phenylethanol in product stream 5 is 99.95%, and the product yield is about 70%. The content of aldehyde and ketone impurities is less than 1ppm, the content of phenolic impurities is less than 1ppm, and the content of 1-phenyl-2-propanol is less than 1ppm. The product odor is evaluated as a soft and lasting rose fragrance.

[0067] Example 3

[0068] A solution stream 2 of thiourea compounds is received at the top of the rotary extractor column, an extractant stream 3 is received in the middle of the column, and a feed stream 1 is received at the bottom. The rotary extractor column has 20 trays and rotates at 100 rpm. Feed stream 1 contains 30 wt% β-phenylethanol, 2 wt% total aldehydes and ketones, 5 wt% phenols, and 1 wt% 1-phenyl-2-propanol, with other components mainly consisting of other alcohols and polymers. The solution stream 2 of thiourea compounds is an ethylbenzene solution of tetramethylthiourea (concentration 5 wt%). The flow rate of feed stream 1 is 1 t / h, and the flow rate of the solution stream 2 is 1000 kg / h (the molar ratio of thiourea compounds in solution stream 2 to aldehydes and ketones in feed stream 1 is approximately 2.3:1). The extractant stream 3 uses ethylbenzene as the extractant, with a flow rate of 1... After impurity removal and extraction, oil phase stream 4 is obtained. Oil phase stream 4 enters a dynamic crystallizer for crystallization. The refrigerant temperature is -50℃ and the heating medium temperature is 25℃. The dynamic crystallization time is controlled by adjusting the flow rate of the refrigerant and heating medium. After crystallization and purification, product stream 5 is obtained. The purity of β-phenylethanol in product stream 5 is 99.97%, and the product yield is about 72%. The content of aldehyde and ketone impurities is less than 1ppm, the content of phenolic impurities is less than 1ppm, and the content of 1-phenyl-2-propanol is less than 1ppm. The product odor is evaluated as a soft and lasting rose fragrance.

[0069]

[0070] Example 4

[0071] A solution stream 2 of thiourea compounds is received at the top of the rotary extractor, an extractant stream 3 is received in the middle of the rotary extractor, and a feed stream 1 is received at the bottom of the rotary extractor. The rotary extractor has 30 trays and rotates at 200 rpm. Feed stream 1 contains 70 wt% β-phenylethanol, 1.5 wt% total aldehydes and ketones, 8 wt% phenols, and 1.2 wt% 1-phenyl-2-propanol; the remaining components are mainly other alcohols and polymers. The solution stream 2 of thiourea compounds is an aqueous solution of 1,3-dimethylthiourea (concentration 70%). The feed stream 1 has a flow rate of 1 t / h, and the solution stream 2 of the thiourea compound has a flow rate of 100 kg / h (the molar ratio of the thiourea compound in the solution stream 2 to the aldehydes and ketones in the feed stream 1 is approximately 5.4:1). The extractant stream 3 uses dichloroethane as the extractant with a flow rate of 1.2 t / h. After impurity removal and extraction, the oil phase stream 4 is obtained. The oil phase stream 4 enters a dynamic crystallizer for crystallization. The coolant temperature is -70℃, the heat medium temperature is 10℃, and the flow rate of the coolant and heat medium is adjusted to control the dynamic crystallization time to 6 h. After crystallization and purification, the product stream 5 is obtained. The product purity of β-phenylethanol in the product stream 5 is 99.96%, and the product yield is approximately 74%. The content of aldehydes and ketones is less than 1 ppm, the content of phenols is less than 1 ppm, and the content of 1-phenyl-2-propanol is less than 1 ppm. The product odor is evaluated as a soft and lasting rose fragrance.

[0072]

[0073] Comparative Example 1

[0074] The solution stream 2 of the thiourea compound is not fed into the rotary extractor. The extractant stream 3 is received in the middle of the rotary extractor, and the feed stream 1 is received at the bottom of the rotary extractor. The rotary extractor has 35 trays and rotates at 200 rpm. The feed stream 1 contains 60 wt% β-phenylethanol, 3 wt% total aldehydes and ketones, 15 wt% phenols, and 2 wt% 1-phenyl-2-propanol. Other components are mainly other alcohols and polymers. The flow rate of feed stream 1 is 1 t / h. Toluene is used as the extractant in extractant stream 3, with a flow rate of 1.5 t / h. After extraction, oil stream 4 is obtained, which enters a dynamic crystallizer for crystallization. The refrigerant temperature is -60℃, the heating medium temperature is 10℃, and the dynamic crystallization time is controlled by adjusting the flow rates of the refrigerant and heating medium for 6 hours. After crystallization and purification, product stream 5 is obtained. The purity of β-phenylethanol in product stream 5 is 99.5%, and the product yield is about 70%. The aldehyde and ketone impurities are much higher than 1 ppm, the phenolic impurities are lower than 1 ppm, the 1-phenyl-2-propanol content is lower than 1 ppm, and the product odor is unacceptable.

[0075]

[0076] Comparative Example 2

[0077] The process was carried out under the same conditions as in Example 2, except that the refrigerant temperature was -30°C and the heat transfer medium temperature was 10°C. The crystallization curves are as follows:

[0078]

[0079] After crystallization and purification, product stream 5 was obtained. The purity of β-phenylethanol in product stream 5 was 92.62%, but the product odor was not up to standard.

[0080]

[0081] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for purifying β-phenylethanol, characterized in that, Raw material stream 1 is the bottom liquid from the dehydration reaction of α-phenylethanol to separate styrene in the ethylbenzene co-oxidation process for producing propylene oxide. The method includes: A solution stream 2 of thiourea compound is received at the upper part of the extraction tower, an extractant stream 3 is received in the middle part of the extraction tower, and a raw material stream 1 is received at the lower part of the extraction tower. The raw material stream 1 is purified and extracted in the extraction tower to obtain an oil phase stream 4. Waste liquid is collected at the bottom of the extraction tower. The oil phase stream 4 is passed into a crystallizer and purified by crystallization to obtain a product stream 5. In this context, the solution stream 2 of the thiourea compound is a solution of the thiourea compound.

2. The method according to claim 1, characterized in that, The thiourea compound is one or more of thiourea, alkylthiourea, aromatic thiourea, and aminothiourea.

3. The method according to claim 2, characterized in that, The thiourea compound is a thiourea or an alkylthiourea.

4. The method according to claim 2, characterized in that, The thiourea compound is one or more of thiourea, tetramethylthiourea, 1,3-dimethylthiourea, ethylthiourea, and diethylthiourea.

5. The method according to claim 2, characterized in that, The thiourea compound solution stream 2 has a mass fraction of 2wt% to 70wt%, and the flow rate to mass ratio of the thiourea compound solution stream 2 to the raw material stream 1 is 1:1 to 1:

10.

6. The method according to claim 5, characterized in that, The flow rate-to-mass ratio of the thiourea compound solution stream 2 to the raw material stream 1 is 1:5 to 1:

8.

7. The method according to claim 5, characterized in that, In the solution stream 2 of the thiourea compound, the molar ratio of the thiourea compound to the aldehydes and ketones in the raw material stream 1 is 1:1 to 8:

1.

8. The method according to claim 7, characterized in that, In the solution stream 2 of the thiourea compound, the molar ratio of the thiourea compound to the aldehydes and ketones in the raw material stream 1 is 1:1 to 3:

1.

9. The method according to claim 2, characterized in that, The solvent in the solution stream 2 of the thiourea compound is water or an organic solvent, or the extractant in the extractant stream 3 is used as the solvent, wherein the organic solvent is one or more of dichloromethane, dichloroethane, toluene, and ethylbenzene.

10. The method according to any one of claims 1-9, characterized in that, The extractant is one or more of dichloromethane, dichloroethane, toluene, and ethylbenzene.

11. The method according to claim 10, characterized in that, The mass ratio of the extractant stream 3 to the raw material stream 1 is 2:1 to 1:

1.

12. The method according to claim 11, characterized in that, The mass ratio of the extractant stream 3 to the raw material stream 1 is 1.5:1 to 1.1:

1.

13. The method according to any one of claims 1-9, characterized in that, The extraction tower is a rotary disc extraction tower.

14. The method according to claim 13, characterized in that, The rotary extraction tower has 15 to 40 rotary discs.

15. The method according to claim 14, characterized in that, The rotary extraction tower has 20 to 35 rotary discs.

16. The method according to claim 5, characterized in that, The total amount of the thiourea compound solution stream 2 is controlled so that the aldehyde and ketone content in the oil phase stream 4 is between 0.1 ppm and 100 ppm.

17. The method according to claim 16, characterized in that, The total amount of the thiourea compound solution stream 2 is controlled so that the aldehyde and ketone content in the oil phase stream 4 is between 1 ppm and 30 ppm.

18. The method according to any one of claims 1-9, characterized in that, The crystallizer is a dynamic crystallizer; And / or, in the crystallization curve of the crystallizer, the endpoint temperature of the cooling process is -40℃ to -45℃; And / or, the refrigerant temperature of the crystallizer is -60℃ to 7℃, and the heat medium temperature is 10℃ to 25℃.

19. The method according to any one of claims 1-9, characterized in that, The impurities contained in the raw material stream 1 are one or more of alcohols, aldehydes, ketones, phenols, and oligomers. The alcohols include one or more of α-phenylethanol, 1-phenyl-2-propanol, and 2-phenyl-1-propanol. The aldehydes include one or more of benzaldehyde, phenylacetaldehyde, acetal, and polyacetal. The phenols include one or more of phenol, ethylphenol, 2,4-xylenol, and 2,6-xylenol, wherein ethylphenol includes one or more of o-ethylphenol, p-ethylphenol, and m-ethylphenol. The oligomers include polystyrene oligomers.

20. The method according to claim 19, characterized in that, The β-phenylethanol content in the raw material stream 1 is 10wt% to 70wt%.

21. The method according to claim 20, characterized in that, The β-phenylethanol content in the raw material stream 1 is 20wt% to 60wt%.

22. The method according to claim 19, characterized in that, The aldehyde content in the raw material stream 1 is 0.1wt% to 3wt%.

23. The method according to claim 22, characterized in that, The aldehyde content in the raw material stream 1 is 0.5wt% to 1wt%.

24. The method according to claim 19, characterized in that, The ketone content in the raw material stream 1 is 0.1wt% to 3wt%.

25. The method according to claim 24, characterized in that, The ketone content in the raw material stream 1 is 0.5wt% to 1wt%.

26. The method according to claim 19, characterized in that, The phenol content in the raw material stream 1 is 0.1 wt% to 15 wt%.

27. The method according to claim 26, characterized in that, The phenol content in the raw material stream 1 is 0.5wt% to 10wt%.

28. The method according to claim 19, characterized in that, The 1-phenyl-2-propanol content in the raw material stream 1 is 0.1 wt% to 2 wt%.

29. The method according to claim 28, characterized in that, The 1-phenyl-2-propanol content in the raw material stream 1 is 0.5 wt% to 1 wt%.

30. The method according to any one of claims 1-9, characterized in that, The β-phenylethanol in product stream 5 has a purity of ≥99.9%, aldehyde content ≤0.01ppm, ketone content ≤1ppm, phenol content ≤1ppm, 1-phenyl-2-propanol content ≤1ppm, and ethylphenol content ≤1ppm.

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