Method for separating alpha-phenethyl alcohol from crude alpha-phenethyl alcohol

Abstract

The invention relates to the technical field of fine chemical engineering, and discloses a method for separating alpha-phenethyl alcohol from a crude product alpha-phenethyl alcohol, which comprises the following steps: 1, carrying out primary rectification on the crude product alpha-phenethyl alcohol to obtain a tower kettle product I with a boiling point of more than 202 DEG C; 2, rectifying the tower kettle product I for the second time to obtain a side product II with the boiling point of 203-206 DEG C; 3, cooling and crystallizing the side product II to obtain a crystallized product; the operation of cooling crystallization comprises first heating and then cooling, the cooling comprises two cooling stages, and the cooling rate of the first stage is higher than that of the second stage; 4, heating and sweating the crystallization product to obtain alpha-phenethyl alcohol crystals; the heating sweating comprises two heating stages, and the heating rate of the first stage is higher than that of the second stage; and 5, heating and melting the alpha-phenethyl alcohol crystal to obtain the alpha-phenethyl alcohol. According to the method provided by the invention, the problem that the phenethyl alcohol and the benzyl alcohol are difficult to separate can be solved, and the alpha-phenethyl alcohol with high yield and high purity can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemicals, and in particular to a method for separating alpha-phenylethanol from crude alpha-phenylethanol. Background Art

[0002] α-Phenylethanol is an aromatic alcohol with the scent of gardenia. It is an important organic chemical raw material and is widely used in the fields of spices, coatings, medicines, synthetic resin solvents, ointment preservatives, fibers and plastic film desiccants.

[0003] Separating α-phenylethanol from crude α-phenylethanol is a common production method of α-phenylethanol. Crude α-phenylethanol is generally tar containing α-phenylethanol generated in a chemical process. For example, chemical processes related to reactions such as dehydrogenation of phenylethanol, hydrolysis of styrene, reaction of benzene and ethylene oxide (propylene oxide), hydrogenation of acetophenone, oxidation of styrene or ethylbenzene (e.g., β-phenylethanol production process by oxidation and hydrogenation of styrene or ethylbenzene) generally generate oil products containing α-phenylethanol, which are generally treated as waste liquid and directly burned. Such a treatment method not only pollutes the environment, but also causes waste of resources.

[0004] If high-purity α-phenylethanol can be separated from crude α-phenylethanol, it can not only reduce the discharge of three wastes, but also significantly increase the added value of the product, generate economic benefits, social benefits and environmental benefits, and lay the foundation for the construction of a "zero-emission" factory. However, crude α-phenylethanol generally also contains benzyl alcohol and acetophenone. α-phenylethanol and benzyl alcohol have similar boiling points, similar structures and properties, and it is difficult to separate and purify the two.

[0005] Therefore, it is urgent to provide a method for separating high-purity α-phenylethanol from crude α-phenylethanol. Summary of the invention

[0006] The purpose of the present invention is to overcome the problem of difficulty in separating α-phenylethanol and benzyl alcohol in the prior art and to provide a method for separating α-phenylethanol from crude α-phenylethanol.

[0007] The present invention provides a method for separating α-phenylethanol from crude α-phenylethanol, wherein the method comprises the following steps:

[0008] (1) subjecting the crude α-phenylethanol to a first distillation to obtain a bottom product I having a boiling point of more than 202° C.;

[0009] (2) subjecting the bottom product I to a second distillation to obtain a side product II having a boiling point of 203-206° C.;

[0010] (3) subjecting the side product II to cooling crystallization to obtain a crystalline product; wherein the cooling crystallization operation includes heating first and then cooling, and the cooling includes two cooling stages, and the cooling rate of the first stage is greater than the cooling rate of the second stage;

[0011] (4) heating the crystallized product to sweat to obtain α-phenylethanol crystals; wherein the heating to sweat comprises two heating stages, and the heating rate of the first stage is greater than the heating rate of the second stage;

[0012] (5) heating and melting the α-phenylethanol crystals to obtain α-phenylethanol.

[0013] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0014] 1) The method for separating α-phenylethanol from crude α-phenylethanol provided in the present invention couples conventional distillation with melt crystallization, and can efficiently separate α-phenylethanol and benzyl alcohol to obtain α-phenylethanol with a purity of more than 99.5%;

[0015] 2) The method for separating α-phenylethanol from crude α-phenylethanol provided in the present invention has high separation efficiency of α-phenylethanol, simple process, low cost and is suitable for industrial promotion. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] The present invention provides a method for separating α-phenylethanol from crude α-phenylethanol, wherein the method comprises the following steps:

[0018] (1) subjecting the crude α-phenylethanol to a first distillation to obtain a bottom product I having a boiling point of more than 202° C.;

[0019] (2) subjecting the bottom product I to a second distillation to obtain a side product II having a boiling point of 203-206° C.;

[0020] (3) subjecting the side product II to cooling crystallization to obtain a crystalline product; wherein the cooling crystallization operation includes heating first and then cooling, and the cooling includes two cooling stages, and the cooling rate of the first stage is greater than the cooling rate of the second stage;

[0021] (4) heating the crystallized product to sweat to obtain α-phenylethanol crystals; wherein the heating to sweat comprises two heating stages, and the heating rate of the first stage is greater than the heating rate of the second stage;

[0022] (5) heating and melting the α-phenylethanol crystals to obtain α-phenylethanol.

[0023] In step (1):

[0024] In a preferred embodiment of the present invention, the crude α-phenylethanol is an oil product containing α-phenylethanol, benzyl alcohol and acetophenone.

[0025] Among them, in the present invention, the crude α-phenylethanol can be an oil product containing α-phenylethanol, benzyl alcohol and acetophenone produced in processes related to reactions such as dehydrogenation reaction of phenylethanol, hydrolysis reaction of styrene, reaction of benzene and ethylene oxide (propylene oxide), hydrogenation reaction of acetophenone, oxidation reaction of styrene or ethylbenzene (for example, process of producing β-phenylethanol by oxidation and hydrogenation of styrene or ethylbenzene).

[0026] In a preferred embodiment of the present invention, the boiling point of the crude α-phenylethanol is 140-320°C, preferably 150-210°C.

[0027] Among them, in the present invention, the oil containing α-phenylethanol, benzyl alcohol and acetophenone generated in the above process can be pretreated to cut out components with a distillation range of 140-320°C, preferably 150-210°C, so as to remove some irrelevant components as much as possible and obtain crude α-phenylethanol with a higher α-phenylethanol content.

[0028] In a preferred embodiment of the present invention, based on the total mass of the crude α-phenylethanol, the crude α-phenylethanol contains 10-90wt% of α-phenylethanol, 1-90wt% of acetophenone, 1-20wt% of benzyl alcohol, 0.1-50wt% of β-phenylethanol, 0.1-20wt% of phenylpropanol and 0.1-20wt% of impurities.

[0029] Wherein, in the present invention, phenylpropanol includes 2-phenyl-1-propanol, 1-phenyl-2-propanol, 2-phenyl-2-propanol, 1-phenyl-1-propanol, 3-phenyl-1-propanol, etc. Impurities can be components such as styrene, ethylphenol (including but not limited to 2-ethylphenol, 3-ethylphenol, 4-ethylphenol), benzaldehyde, phenylacetaldehyde, 1,1-dimethyl-1H-indene, 3,3-dimethyl-1-indanol, etc.

[0030] In a preferred embodiment of the present invention, the first distillation is carried out in a first distillation tower; wherein the operating conditions of the first distillation include: tower top temperature of 40-100°C, preferably 50-80°C; tower bottom temperature of 80-160°C, preferably 90-135°C; tower top pressure of 0.1-5kPa, preferably 0.2-3kPa; tower bottom pressure of 0.2-10kPa, preferably 0.3-5kPa.

[0031] Among them, in the present invention, the boiling points of acetophenone, α-phenylethanol and acetophenone are close (202-204° C.), and the crude α-phenylethanol is subjected to the first distillation, so that most of the acetophenone can be separated from the crude α-phenylethanol to obtain the bottom product I mainly containing α-phenylethanol and benzyl alcohol, and a small amount of acetophenone.

[0032] In a preferred embodiment of the present invention, the operating conditions of the first distillation also include: the number of theoretical plates is 20-80, preferably 40-60; the number of feed plates of crude α-phenylethanol is 5-30, preferably 8-15; the number of side product extraction plates is 1-15, preferably 3-8; the reflux ratio is 2-12, preferably 6-10.

[0033] Among them, in the present invention, the crude α-phenylethanol is introduced into the first distillation tower for the first distillation, and the crude α-phenylethanol can be cut into two parts, and the components with a boiling point of more than 202°C, mainly containing α-phenylethanol and benzyl alcohol, and a small amount of acetophenone are extracted from the bottom of the tower, and the remaining parts are all extracted from the top of the tower. In addition, the present invention can also cut the crude α-phenylethanol into three parts, extract the bottom product I with a boiling point of more than 202°C, mainly containing α-phenylethanol and benzyl alcohol, and a small amount of acetophenone from the bottom of the tower, extract the side line product I (acetophenone) with a boiling point of 202°C from the side line, and the part with a boiling point of less than 202°C is all extracted from the top of the tower, thereby obtaining the top product I.

[0034] In step (2):

[0035] In a preferred embodiment of the present invention, the second distillation is carried out in a second distillation tower, wherein the distillation operating conditions of the second distillation include: tower top temperature of 50-110°C, preferably 55-100°C; tower bottom temperature of 90-180°C, preferably 110-160°C; tower top pressure of 0.1-5kPa, preferably 0.2-3kPa; tower bottom pressure of 0.2-10kPa, preferably 0.3-5kPa.

[0036] Among them, in the present invention, it is difficult to completely separate acetophenone by a single distillation, and a second distillation of the bottom product I can further separate acetophenone, thereby improving the purity of the target product α-phenylethanol.

[0037] In a preferred embodiment of the present invention, the distillation operating conditions of the second distillation also include: the number of theoretical plates is 20-80, preferably 60-70; the number of feed plates of the second distillation tower bottom product is 6-35, preferably 15-25; the number of side product extraction plates is 1-30, preferably 10-15; the reflux ratio is 4-12, preferably 7-10.

[0038] Wherein, in the present invention, the tower bottom product I is introduced into the second distillation tower for the second distillation, and the tower bottom product I can be cut into three parts, and the components with a boiling point of less than 203°C are extracted from the tower top for separating acetophenone. Under the premise of ensuring that the acetophenone is separated as completely as possible, a small amount of α-phenylethanol and benzyl alcohol are allowed to be extracted from the tower top together with acetophenone. The side line extraction is to further obtain a high-purity mixture of α-phenylethanol and benzyl alcohol. The components with a boiling point of more than 206°C are extracted from the tower bottom for separating a small amount of remaining components other than acetophenone, α-phenylethanol and benzyl alcohol contained in the tower bottom product I. In order to improve the purity of α-phenylethanol and benzyl alcohol in the side line product II as much as possible, a small amount of α-phenylethanol and benzyl alcohol are allowed to be extracted from the tower bottom.

[0039] In step (3):

[0040] In a preferred embodiment of the present invention, the heating temperature is 25-50°C, preferably 30-35°C.

[0041] In a preferred embodiment of the present invention, the cooling rate of the first stage is 0.1-0.2°C / min, preferably 0.14-0.18°C / min; the final temperature of the first stage is 20-25°C, preferably 20-22°C.

[0042] In a preferred embodiment of the present invention, the cooling rate of the second stage is 0.05-0.1°C / min, preferably 0.05-0.08°C / min; the final temperature of the second stage is 10-15°C, preferably 11-14°C; the final temperature holding time of the second stage is 2.5-4h, preferably 3-3.5h.

[0043] In the process of cooling crystallization, α-phenylethanol and a small amount of benzyl alcohol in the side product II are slowly converted into crystals, thereby precipitating from the side product II. After the cooling crystallization is completed, the crystallization mother liquor is discharged to obtain a crystalline product containing α-phenylethanol and a small amount of benzyl alcohol. By controlling the cooling rate of the two cooling stages, it is possible to ensure that all α-phenylethanol crystals are precipitated as much as possible, and reduce the amount of benzyl alcohol crystals precipitated.

[0044] In step (4):

[0045] In a preferred embodiment of the present invention, the heating rate of the first stage is 0.02-0.08°C / min, preferably 0.05-0.07°C / min; the final temperature of the first stage is 18-22°C, preferably 19-21°C; the final temperature holding time of the first stage is 0.5-3h, preferably 1-2h.

[0046] In a preferred embodiment of the present invention, the heating rate of the second stage is 0.01-0.06°C / min, preferably 0.02-0.05°C / min; the final temperature of the second stage is 30-35°C, preferably 32-34°C.

[0047] In the process of sweating during heating, most of the α-phenylethanol crystals continue to exist in the form of crystals, while the benzyl alcohol crystals are transformed into liquid to form sweating liquid. After the sweating is completed, the sweating liquid is discharged, so that high-purity α-phenylethanol crystals can be obtained. By controlling the heating rates of the two heating stages, it is possible to ensure that all α-phenylethanol crystals are transformed into liquid as much as possible, and to minimize the liquefaction of α-phenylethanol crystals.

[0048] In step (5):

[0049] In a preferred embodiment of the present invention, the melting temperature of the heating and melting is 40-65°C, preferably 45-55°C.

[0050] In the present invention, the α-phenylethanol crystals can be melted into a liquid that is convenient for storage and transportation by heating and melting. The α-phenylethanol after heating and melting is a colorless and transparent liquid with a purity of ≥99.9% and a yield of ≥50%, preferably 55-80%.

[0051] In a preferred embodiment of the present invention, the temperature-drop crystallization, temperature-up sweating and temperature-up melting are carried out in a melt crystallizer. Preferably, the melt crystallizer is selected from a high-efficiency static melt crystallizer and / or a dynamic tower falling film melt crystallizer.

[0052] Among them, in the present invention, the cooling crystallization, heating sweating and heating melting can be carried out in the same melt crystallizer, or in different melt crystallizers, preferably in the same melt crystallizer.

[0053] The present invention will be described in detail below by way of examples.

[0054] In the crude α-phenylethanol in the embodiment, the content of α-phenylethanol is 32wt%, the content of acetophenone is 65wt%, the content of benzyl alcohol is 1wt%, the content of β-phenylethanol is 0.2wt%, the content of phenylpropanol is 0.1wt%, and the content of impurities is 1.7wt% (the impurities include 0.8wt% of 3,3-dimethyl-1-indanol, 0.1wt% of phenylacetaldehyde and 0.8wt% of benzaldehyde).

[0055] Example 1

[0056] (1) introducing the crude α-phenylethanol from the 12th theoretical plate into the first distillation tower for the first distillation, taking out the top product I with a boiling point of less than 202° C. from the top of the first distillation tower, taking out the side product I acetophenone from the side line of the first distillation tower, and taking out the bottom product I with a boiling point of more than 202° C. from the bottom of the first distillation tower;

[0057] Among them, the top temperature of the first distillation tower is 68°C, the bottom temperature is 135°C, the top pressure is 1.2kPa, the bottom pressure is 2.0kPa, the theoretical plate number is 60, the side line theoretical plate number is 8, and the reflux ratio is 10;

[0058] (2) introducing the bottom product I from the 15th theoretical plate into a second distillation tower for a second distillation, taking a top product II with a boiling point of less than 203° C. from the top of the second distillation tower, taking a side product II with a boiling point of 203° C. <206° C. from the side line of the second distillation tower, and taking a bottom product II with a boiling point of more than 206° C. from the bottom of the second distillation tower;

[0059] Among them, the top temperature of the second distillation tower is 55°C, the bottom temperature is 110°C, the top pressure is 0.2kPa, the bottom pressure is 0.3kPa, the theoretical plate number is 70, the side line theoretical plate number is 10, and the reflux ratio is 7;

[0060] (3) introducing the side product II into a melt crystallizer for cooling and crystallization treatment, first heating to 35°C, then cooling to 20°C at a rate of 0.18°C / min, and then further cooling to 14°C at a rate of 0.05°C / min. After maintaining the constant temperature for 3.5 hours, the crystallization mother liquor was discharged to obtain a crystallized product;

[0061] (4) heating the crystallized product in a melt crystallizer to sweat, heating the temperature to 20° C. at a rate of 0.05° C. / min, and maintaining the temperature for 2 h; then heating the temperature to 34° C. at a rate of 0.02° C. / min, and then discharging the sweating liquid from the melt crystallizer to obtain α-phenylethanol crystals;

[0062] (5) heating the α-phenylethanol crystals to 45° C. in a melt crystallizer to melt the α-phenylethanol crystals to obtain α-phenylethanol;

[0063] Among them, α-phenylethanol is a colorless and transparent liquid with a purity of 99.90% and a yield of 78.1%.

[0064] Example 2

[0065] (1) introducing the crude α-phenylethanol from the 8th theoretical plate into the first distillation tower for the first distillation, taking the top product I with a boiling point of less than 202° C. from the top of the first distillation tower, taking acetophenone I from the side line of the first distillation tower, and taking the bottom product I with a boiling point of more than 202° C. from the bottom of the first distillation tower;

[0066] The top temperature of the first distillation tower is 50°C, the bottom temperature is 90°C, the top pressure is 0.2kPa, the bottom pressure is 0.3kPa, the theoretical plate number is 40, the side line theoretical plate number is 3, and the reflux ratio is 6;

[0067] (2) introducing the bottom product I from the 20th theoretical plate into a second distillation tower for a second distillation, taking a top product II with a boiling point of less than 203° C. from the top of the second distillation tower, taking a side product II with a boiling point of 203° C. <206° C. from the side line of the second distillation tower, and taking a bottom product II with a boiling point of more than 206° C. from the bottom of the second distillation tower;

[0068] Among them, the top temperature of the second distillation tower is 100°C, the bottom temperature is 160°C, the top pressure is 3kPa, the bottom pressure is 5kPa, the theoretical plate number is 60, the side line theoretical plate number is 15, and the reflux ratio is 10;

[0069] (3) introducing the side product II into a melt crystallizer for cooling and crystallization treatment, first heating to 30°C, then cooling to 22°C at a rate of 0.14°C / min, and then further cooling to 11°C at a rate of 0.08°C / min. After maintaining the constant temperature for 3 hours, the crystallization mother liquor was discharged to obtain a crystallized product;

[0070] (4) heating the crystallized product in a melt crystallizer to sweat, heating the temperature to 21° C. at a rate of 0.07° C. / min, and maintaining the temperature for 1 hour; then, heating the temperature to 32° C. at a rate of 0.05° C. / min, and then discharging the sweating liquid from the melt crystallizer to obtain α-phenylethanol crystals;

[0071] (5) heating the α-phenylethanol crystals to 45° C. in a melt crystallizer to melt the α-phenylethanol crystals to obtain α-phenylethanol;

[0072] Among them, α-phenylethanol is a colorless and transparent liquid with a purity of 99.92% and a yield of 70.4%.

[0073] Example 3

[0074] (1) introducing the crude α-phenylethanol into the first distillation tower from the 15th theoretical plate for the first distillation, taking out the top product I with a boiling point of less than 202° C. from the top of the first distillation tower, taking out acetophenone I from the side line of the first distillation tower, and taking out the bottom product I with a boiling point of more than 202° C. from the bottom of the first distillation tower;

[0075] The top temperature of the first distillation tower is 80°C, the bottom temperature is 150°C, the top pressure is 3kPa, the bottom pressure is 5kPa, the theoretical plate number is 60, the side line theoretical plate number is 4, and the reflux ratio is 8;

[0076] (2) introducing the bottom product I from the 25th theoretical plate into a second distillation tower for a second distillation, taking a top product II with a boiling point of less than 203° C. from the top of the second distillation tower, taking a side product II with a boiling point of 203° C. <206° C. from the side line of the second distillation tower, and taking a bottom product II with a boiling point of more than 206° C. from the bottom of the second distillation tower;

[0077] Among them, the top temperature of the second distillation tower is 59°C, the bottom temperature is 90°C, the top pressure is 0.2kPa, the bottom pressure is 0.3kPa, the theoretical plate number is 45, the side line theoretical plate number is 5, and the reflux ratio is 8;

[0078] (3) introducing the side product II into a melt crystallizer for cooling and crystallization treatment, first heating to 32° C., then cooling to 21° C. at a rate of 0.16° C. / min, and then further cooling to 12° C. at a rate of 0.06° C. / min. After maintaining the constant temperature for 3.2 h, the crystallization mother liquor was discharged to obtain a crystallized product;

[0079] (4) heating the above-mentioned crystal product in a melt crystallizer to sweat, heating it to 19° C. at a rate of 0.06° C. / min, and maintaining the constant temperature for 1.5 h; then continuing to heat it to 33° C. at a heating rate of 0.04° C. / min, and then discharging the sweating liquid from the melt crystallizer to obtain α-phenylethanol crystals;

[0080] (5) heating the α-phenylethanol crystals to 45° C. in a melt crystallizer to melt the α-phenylethanol crystals to obtain α-phenylethanol;

[0081] Among them, α-phenylethanol is a colorless and transparent liquid with a purity of 99.81% and a yield of 63.4%.

[0082] Comparative Example 1

[0083] (1) 200 kg of crude α-phenylethanol is introduced into the first distillation tower from the 12th theoretical plate for the first distillation, 18 kg / h of the top product I with a boiling point of less than 202° C. is produced from the top of the first distillation tower, 100 kg / h of the side product I acetophenone is produced from the side line of the first distillation tower, and 82 kg / h of the bottom product I with a boiling point of more than 202° C. is produced from the bottom of the first distillation tower;

[0084] Among them, the top temperature of the first distillation tower is 68°C, the bottom temperature is 127°C, the top pressure is 1.2kPa, the bottom pressure is 2.0kPa, the theoretical plate number is 60, the side line theoretical plate is 8, and the reflux ratio is 10;

[0085] (2) introducing the above-mentioned bottom product I into a melt crystallizer for cooling crystallization treatment, first heating to 35°C, then cooling to 20°C at a rate of 0.18°C / min, and then further cooling to 14°C at a rate of 0.05°C / min. After maintaining the constant temperature for 3.5 hours, the crystallization mother liquor is discharged to obtain a crystalline product;

[0086] (3) heating the above-mentioned crystal product in a melt crystallizer to sweat, heating it to 20° C. at a rate of 0.05° C. / min, and maintaining the constant temperature for 2 h; then continuing to heat it to 34° C. at a rate of 0.02° C. / min, and then discharging the sweating liquid from the melt crystallizer to obtain α-phenylethanol crystals;

[0087] (4) heating the α-phenylethanol crystals to 45° C. in a melt crystallizer to melt the α-phenylethanol crystals to obtain α-phenylethanol;

[0088] Among them, α-phenylethanol is a colorless and transparent liquid with a purity of 92.46% and a yield of 55.3%.

[0089] Comparative Example 2

[0090] (1) 200 kg of crude α-phenylethanol is introduced into the first distillation tower from the 12th theoretical plate for the first distillation, 18 kg / h of the top product I with a boiling point of less than 202° C. is produced from the top of the first distillation tower, 100 kg / h of the side product I acetophenone is produced from the side line of the first distillation tower, and 82 kg / h of the bottom product I with a boiling point of more than 202° C. is produced from the bottom of the first distillation tower;

[0091] Among them, the top temperature of the first distillation tower is 68°C, the bottom temperature is 127°C, the top pressure is 1.2kPa, the bottom pressure is 2.0kPa, the theoretical plate number is 60, the side line theoretical plate is 8, and the reflux ratio is 10;

[0092] (2) The bottom product I is introduced into the second distillation tower from the 15th theoretical plate for a second distillation, and 14 kg / h of the top product II with a boiling point of <203° C. is produced from the top of the second distillation tower, 55 kg / h of the side product II with a boiling point of 203° C. <206° C. is produced from the side line of the second distillation tower, and 13 kg / h of the bottom product II with a boiling point of >206° C. is produced from the bottom of the second distillation tower;

[0093] Among them, the top temperature of the second distillation tower is 55°C, the bottom temperature is 110°C, the top pressure is 0.2kPa, the bottom pressure is 0.3kPa, the theoretical plate number is 40, the side line theoretical plate number is 10, and the reflux ratio is 7;

[0094] (3) introducing the side product II into a melt crystallizer for cooling and crystallization treatment, heating to 35° C., then cooling to 14° C. at a rate of 0.18° C. / min, maintaining the constant temperature for 3.5 h, and then discharging the crystallization mother liquor to obtain a crystallized product;

[0095] (4) heating the crystallized product in a melt crystallizer to sweat, heating the temperature to 20° C. at a rate of 0.05° C. / min, and maintaining the temperature for 2 h; then heating the temperature to 34° C. at a rate of 0.02° C. / min, and then discharging the sweating liquid from the melt crystallizer to obtain α-phenylethanol crystals;

[0096] (5) heating the α-phenylethanol crystals to 45° C. in a melt crystallizer to melt the α-phenylethanol crystals to obtain α-phenylethanol;

[0097] Among them, α-phenylethanol is a colorless and transparent liquid with a purity of 98.14% and a yield of 57.79%.

[0098] Comparative Example 3

[0099] (1) 200 kg of crude α-phenylethanol is introduced into the first distillation tower from the 12th theoretical plate for the first distillation, 18 kg / h of the top product I with a boiling point of less than 202° C. is produced from the top of the first distillation tower, 100 kg / h of the side product I acetophenone is produced from the side line of the first distillation tower, and 82 kg / h of the bottom product I with a boiling point of more than 202° C. is produced from the bottom of the first distillation tower;

[0100] Among them, the top temperature of the first distillation tower is 68°C, the bottom temperature is 127°C, the top pressure is 1.2kPa, the bottom pressure is 2.0kPa, the theoretical plate number is 60, the side line theoretical plate is 8, and the reflux ratio is 10;

[0101] (2) The bottom product I is introduced into the second distillation tower from the 15th theoretical plate for a second distillation, and 14 kg / h of the top product II with a boiling point of <203° C. is produced from the top of the second distillation tower, 55 kg / h of the side product II with a boiling point of 203° C. <206° C. is produced from the side line of the second distillation tower, and 13 kg / h of the bottom product II with a boiling point of >206° C. is produced from the bottom of the second distillation tower;

[0102] Among them, the top temperature of the second distillation tower is 55°C, the bottom temperature is 110°C, the top pressure is 0.2kPa, the bottom pressure is 0.3kPa, the theoretical plate number is 40, the side line theoretical plate number is 10, and the reflux ratio is 7;

[0103] (3) introducing the side product II into a melt crystallizer for cooling and crystallization treatment, first heating to 35°C, then cooling to 20°C at a rate of 0.18°C / min, and then further cooling to 14°C at a rate of 0.05°C / min. After maintaining the constant temperature for 3.5 hours, the crystallization mother liquor was discharged to obtain a crystallized product;

[0104] (4) heating the above-mentioned crystal product in a melt crystallizer to sweat, raising the temperature to 34° C. at a rate of 0.05° C. / min, and maintaining the constant temperature for 2 hours; then discharging the sweating liquid from the melt crystallizer to obtain α-phenylethanol crystals;

[0105] (5) heating the α-phenylethanol crystals to 45° C. in a melt crystallizer to melt the α-phenylethanol crystals to obtain α-phenylethanol;

[0106] Among them, α-phenylethanol is a colorless and transparent liquid with a purity of 98.28% and a yield of 56.35%.

[0107] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for separating α-phenylethanol from crude α-phenylethanol, characterized in that: The method comprises the following steps: (1) subjecting the crude α-phenylethanol to a first distillation to obtain a bottom product I having a boiling point of more than 202° C.; (2) subjecting the bottom product I to a second distillation to obtain a side product II having a boiling point of 203-206° C.; (3) subjecting the side product II to cooling crystallization to obtain a crystalline product; wherein the cooling crystallization operation includes heating first and then cooling, and the cooling includes two cooling stages, and the cooling rate of the first stage is greater than the cooling rate of the second stage; (4) heating the crystallized product to sweat to obtain α-phenylethanol crystals; wherein the heating to sweat comprises two heating stages, and the heating rate of the first stage is greater than the heating rate of the second stage; (5) heating and melting the α-phenylethanol crystals to obtain α-phenylethanol.

2. The method according to claim 1, wherein: The crude α-phenylethanol is an oil product containing α-phenylethanol, benzyl alcohol and acetophenone; Preferably, based on the total mass of the crude α-phenylethanol, the crude α-phenylethanol contains 10-90wt% of α-phenylethanol, 1-90wt% of acetophenone, 1-20wt% of benzyl alcohol, 0.1-50wt% of β-phenylethanol, 0.1-20wt% of phenylpropanol and 0.1-20wt% of impurities.

3. The method according to claim 1, wherein: The first distillation is carried out in a first distillation tower; wherein the operating conditions of the first distillation include: a tower top temperature of 40-100°C, preferably 50-80°C; a tower bottom temperature of 80-160°C, preferably 90-135°C; a tower top pressure of 0.1-5kPa, preferably 0.2-3kPa; a tower bottom pressure of 0.2-10kPa, preferably 0.3-5kPa.

4. The method according to claim 3, wherein: The operating conditions of the first distillation also include: the number of theoretical plates is 20-80, preferably 40-60; the number of feed plates of crude α-phenylethanol is 5-30, preferably 8-15; the number of side product extraction plates is 1-15, preferably 3-8; and the reflux ratio is 2-12, preferably 6-10.

5. The method according to claim 1, wherein: The second distillation is carried out in a second distillation tower; wherein the distillation operating conditions of the second distillation tower include: a tower top temperature of 50-110°C, preferably 55-100°C; a tower bottom temperature of 90-180°C, preferably 110-160°C; a tower top pressure of 0.1-5kPa, preferably 0.2-3kPa; a tower bottom pressure of 0.2-10kPa, preferably 0.3-5kPa.

6. The method according to claim 5, wherein: The distillation operating conditions of the second distillation tower also include: the number of theoretical plates is 20-80, preferably 60-70; the number of feed plates for the second distillation tower bottom product is 6-35, preferably 15-25; the number of side product extraction plates is 1-30, preferably 10-15; the reflux ratio is 4-12, preferably 7-10.

7. The method according to claim 1, wherein: The heating temperature is 25-50°C, preferably 30-35°C.

8. The method according to claim 1, wherein: The cooling rate of the first stage is 0.1-0.2°C / min, preferably 0.14-0.18°C / min; the final temperature of the first stage is 20-25°C, preferably 20-22°C; Preferably, the cooling rate of the second stage is 0.05-0.1°C / min, preferably 0.05-0.08°C / min; the final temperature of the second stage is 10-15°C, preferably 11-14°C; the final temperature holding time of the second stage is 2.5-4h, preferably 3-3.5h.

9. The method according to claim 1, wherein: The heating rate of the first stage is 0.02-0.08°C / min, preferably 0.05-0.07°C / min; the final temperature of the first stage is 18-22°C, preferably 19-21°C; the final temperature holding time of the first stage is 0.5-3h, preferably 1-2h; Preferably, the heating rate of the second stage is 0.01-0.06°C / min, preferably 0.02-0.05°C / min; the final temperature of the second stage is 30-35°C, preferably 32-34°C.

10. The method according to claim 1, wherein: The temperature of the heating and melting is 40-65°C, preferably 45-55°C.