Method for separating 2-methyl-6-propionyl naphthalene through melt crystallization

Abstract

The invention provides a method for separating 2-methyl-6-propionyl naphthalene through melt crystallization, which comprises the following steps: reacting 2-methylnaphthalene with propionic anhydride under the action of a catalyst to obtain a 2-methyl-propionyl naphthalene mixture; the 2-methyl-propionyl naphthalene mixture is distilled, and a 2-methyl-propionyl naphthalene crude product is obtained; and carrying out melt crystallization on the 2-methyl-acyl naphthalene crude product to obtain the 2-methyl-6-propionyl naphthalene. According to the method for separating the 2-methyl-6-propionyl naphthalene through melt crystallization, after the crude product of the 2-methyl-6-propionyl naphthalene is obtained through distillation and purification, the high-purity 2-methyl-6-propionyl naphthalene can be obtained through a melt crystallization one-step method. The method has the advantages of simple process operation, high separation efficiency, low energy consumption, high product purity and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a method for separating 2-methyl-6-propionyl naphthalene by melt crystallization. BACKGROUND

[0002] 2,6-naphthalene dicarboxylic acid (2,6-NDA) is an important intermediate for manufacturing high-strength, well-dyed polyester fibers and F-grade insulating materials, and is also widely used in the fields of dyes and medicines. The molecular structure of 2,6-naphthalene dicarboxylic acid is highly symmetrical. The polyethylene glycol 2,6-naphthalene dicarboxylate (PEN) obtained by reacting with ethylene glycol has the characteristics of linear polymers, and is a high-performance material with good rigidity, high strength and excellent thermal processing performance.

[0003] 2-methyl-6-acyl naphthalene is an important chemical substance, which can be used as a precursor of 2,6-naphthalene dicarboxylic acid. The synthesis of 2-methyl-6-acyl naphthalene is mainly a Friedel-Crafts acylation reaction with 2-methylnaphthalene (2-MN) as the reactant, using traditional Lewis as the catalyst, and reacting in a homogeneous solution system. The selectivity of the reaction is good, and high-purity products can be obtained after solvent recovery and recrystallization. However, due to the large number of isomers (7 kinds), the energy consumption and the amount of solvent used are large during separation, and the product loss in the mother liquor is large. Among the 7 isomers of 2-methyl-propionyl naphthalene, the boiling point and polarity of 2-methyl-6-propionyl naphthalene are similar to those of 2-methyl-7-propionyl naphthalene (compared with the other 5 isomers), so it is difficult to obtain high-purity 2-methyl-6-propionyl naphthalene by one-step method.

[0004] In addition, the related art mainly uses a method combining vacuum distillation and recrystallization to separate and purify 2-methyl-6-propionyl naphthalene. The separation of 2-methyl-6-propionyl naphthalene and 2-methyl-7-propionyl naphthalene needs to be completed by recrystallization, and the last step of obtaining 2-methyl-6-propionyl naphthalene with a purity of ≥98.0% causes a large amount of recrystallization solvent to be used, and the repeatability is poor. SUMMARY

[0005] Therefore, the present application aims to provide a method for separating 2-methyl-6-propionyl naphthalene by melt crystallization. After obtaining 2-methyl-acyl naphthalene crude product by distillation purification, high-purity 2-methyl-6-propionyl naphthalene can be obtained by one-step melt crystallization. The method has the advantages of simple process operation, high separation efficiency, low energy consumption, and high product purity.

[0006] To achieve the above-mentioned purpose, the present application provides a method for separating 2-methyl-6-propionyl naphthalene by melt crystallization, comprising: reacting 2-methyl naphthalene and propionic anhydride under the action of a catalyst to obtain a 2-methyl-propionyl naphthalene mixture; The mixture of 2-methyl-propionylnaphthalene was distilled to obtain crude 2-methyl-acylnaphthalene. The crude 2-methyl-acylnaphthalene was melt-crystallized to obtain 2-methyl-6-propionylnaphthalene.

[0007] In some embodiments, the melt crystallization is carried out in a tubular melt crystallizer.

[0008] In some embodiments, the melt crystallization includes: The crude 2-methyl-acylnaphthalene product is cooled to a first temperature at a first rate and then subjected to a first heat preservation. The material after the first heat preservation is subjected to a first filtration to separate the mother liquor, followed by sweating, a second filtration, and a second heating.

[0009] In some embodiments, the sweating process includes: first heating to a second temperature at a second rate and then performing a second heat preservation.

[0010] In some implementations, the first rate is 0.5-2 °C / h.

[0011] In some embodiments, the first temperature is 38-42°C.

[0012] In some implementations, the first heat preservation time is 0.5-2 hours.

[0013] In some embodiments, the second rate is 0.5-3.5 °C / h.

[0014] In some embodiments, the second temperature is 59-62°C.

[0015] In some embodiments, the second heat preservation time is 0.5-2 hours.

[0016] In some embodiments, the termination temperature of the second heating is the temperature at which the crystal layer completely melts.

[0017] In some embodiments, the melt crystallization further includes the steps of opening the bottom discharge valve of the melt crystallization system after the first heat preservation and closing the bottom discharge valve of the melt crystallization system after the second filtration.

[0018] In some embodiments, the catalyst comprises a supported molecular sieve catalyst; the supported molecular sieve catalyst comprises a support and an active component, the support comprising a zeolite molecular sieve, and the active component comprising ferric chloride and aluminum chloride.

[0019] In some embodiments, the reaction is a heterogeneous catalytic synthesis reaction.

[0020] In some embodiments, the mass ratio of ferric chloride to aluminum chloride in the active component is (2-4):(1-3).

[0021] In some embodiments, the zeolite molecular sieve includes at least one of MCM-22 and SAPO-11.

[0022] In some embodiments, the method for preparing the supported molecular sieve catalyst includes: The carrier is pretreated to obtain a pretreated carrier; The active component is dispersed in an organic solvent to obtain a dispersion; The pretreated carrier is added to the dispersion, followed by stirring and reflux, third filtration, drying, grinding, and calcination to obtain the supported molecular sieve catalyst.

[0023] In some embodiments, the pretreatment temperature is 550-650°C, and the pretreatment time is 2-4 hours.

[0024] In some embodiments, the organic solvent includes at least one of chloroform, nitrobenzene, and dichloroethane.

[0025] In some embodiments, the temperature of the stirring reflux is 50.0-90.0°C, and the stirring reflux time is 1.0-3.0 h.

[0026] In some embodiments, the calcination temperature is 500-600°C, and the calcination time is 2-4 hours.

[0027] In some embodiments, the molar ratio of 2-methylnaphthalene to propionic anhydride is 1:(1.5-2.5).

[0028] In some embodiments, the amount of catalyst added is 13.5-15.5% of the total mass of the 2-methylnaphthalene and propionic anhydride.

[0029] In some embodiments, the reaction temperature is 180-200°C and the reaction time is 10-14 hours.

[0030] In some embodiments, the purity of the 2-methyl-6-propionylnaphthalene is above 99.0 wt%.

[0031] In some embodiments, the distillation is vacuum distillation.

[0032] In some embodiments, the distillation includes: The 2-methyl-propionylnaphthalene mixture was subjected to a first distillation to remove unreacted propionic acid, propionic anhydride, and a small amount of 2-methylnaphthalene; The product after the first distillation was subjected to a second distillation to obtain crude 2-methyl-acylnaphthalene.

[0033] In some embodiments, the temperature of the first distillation is 115-117°C, and the pressure of the first distillation is 3.4-4.2 kPa.

[0034] In some embodiments, the temperature of the second distillation is 185-188°C, and the pressure of the second distillation is 2.5-3.2 kPa.

[0035] The method for separating 2-methyl-6-propionylnaphthalene by melt crystallization described in this application can bring at least the following beneficial effects: 1. By combining distillation and melt crystallization, 2-methyl-acylnaphthalene is purified in one step through a systematic melt crystallization operation, resulting in 2-methyl-6-propionylnaphthalene with extremely high purity (above 99.0 wt%), which is difficult to achieve by solution recrystallization separation method. Moreover, the melt crystallization operation is simple and has low energy consumption.

[0036] 2. A mixture of 2-methyl-propionylnaphthalene is synthesized by heterogeneous catalysis using green molecular sieves as raw material. This method differs from the traditional Lewis acid homogeneous catalyst synthesis method, avoids the generation of large amounts of acidic wastewater from hydrolysis, and allows for catalyst recycling.

[0037] 3. Compared with the insulated suction funnel, the tubular static melting crystallizer is simple to operate, and the crystallization temperature, cooling rate and crystallization time are precisely controlled with high repeatability.

[0038] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0039] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings. in: Figure 1 The flowchart illustrates a method for separating 2-methyl-6-propionylnaphthalene by melt crystallization, which is an exemplary embodiment of this application. Detailed Implementation

[0040] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0041] In this application, the disclosure of numerical ranges includes all values ​​throughout the range and the disclosure of further subdivisions of the range, including the endpoints and subranges given for these ranges.

[0042] Unless otherwise specified, all raw materials and equipment involved in this application are self-made through commercial means or known methods; and all methods involved are conventional methods unless otherwise specified.

[0043] When the term “and / or” is used in a list containing two or more items, it means that any of the listed items can be used alone or in combination with any one or more of the listed items. For example, the expression “A and / or B” is intended to mean A or B or A and B, that is, A only, B only, or a combination of A and B.

[0044] The inventors discovered that current technologies for synthesizing 2-methyl-6-propionylnaphthalene mostly employ the Lewis acid homogeneous catalyst synthesis method. This reaction requires hydrolysis quenching, generating large amounts of acidic wastewater, which necessitates solvent recovery, resulting in high energy consumption and solvent usage, as well as significant product loss in the mother liquor. Furthermore, the separation and purification of 2-methyl-6-propionylnaphthalene often utilizes a combination of vacuum distillation and recrystallization. The separation of 2-methyl-6-propionylnaphthalene from 2-methyl-7-propionylnaphthalene requires recrystallization to obtain the final step of 2-methyl-6-propionylnaphthalene with a purity ≥98.0%, leading to excessive use of recrystallization solvent and poor reproducibility.

[0045] Building upon the above findings, the inventors further discovered that by using 2-methylnaphthalene as a raw material and employing heterogeneous catalysis via green molecular sieves to synthesize a mixture of 2-methyl-propionylnaphthalene, a simple 2-methyl-propionylnaphthalene isomer is obtained. This is then purified by distillation to obtain crude 2-methyl-acylnaphthalene, which is further purified by a one-step melt crystallization method to yield high-purity (above 99.0 wt%) 2-methyl-6-propionylnaphthalene. This method offers advantages such as simple operation, high separation efficiency, low energy consumption, and high product purity. Furthermore, melt crystallization can yield a 6-position 2-methyl-6-acylnaphthalene product with extremely high purity (above 99.0 wt%), which can be further oxidized to obtain high-purity 2,6-NDA, providing a new route for the synthesis of high-purity 2,6-NDA.

[0046] A method for separating 2-methyl-6-propionylnaphthalene by melt crystallization according to an embodiment of this application is described below with reference to the accompanying drawings.

[0047] Figure 1 The flowchart illustrates a method for separating 2-methyl-6-propionylnaphthalene by melt crystallization, which is an exemplary embodiment of this application.

[0048] like Figure 1 As shown, the method for separating 2-methyl-6-propionylnaphthalene by melt crystallization in this application includes the following steps: S101. 2-Methylnaphthalene and propionic anhydride are reacted under the action of a catalyst to obtain a mixture of 2-methyl-propionylnaphthalene.

[0049] In some embodiments, the reaction is a heterogeneous catalytic synthesis reaction.

[0050] In some embodiments, the reaction temperature is 180-200°C, including but not limited to 185°C, 190°C or 195°C, preferably 190°C.

[0051] In some embodiments, the reaction time is 10-14 hours, including but not limited to 11 hours, 12 hours or 13 hours, preferably 12 hours.

[0052] In the embodiments of this application, the equation for the reaction is: .

[0053] In some embodiments, the molar ratio of 2-methylnaphthalene to propionic anhydride is 1:(1.5-2.5), including but not limited to 1:1.75, 1:2 or 1:2.25, preferably 1:2.

[0054] In some embodiments, the amount of catalyst added is 13.5-15.5% of the total mass of the 2-methylnaphthalene and propionic anhydride, for example, 14%.

[0055] In some embodiments, the catalyst comprises a supported molecular sieve catalyst; the supported molecular sieve catalyst comprises a support and an active component, the support comprising a zeolite molecular sieve, and the active component comprising ferric chloride (FeCl3) and aluminum chloride (AlCl3).

[0056] As an optional example, the catalyst is a supported molecular sieve catalyst; the supported molecular sieve catalyst consists of a support and an active component, wherein the support is a zeolite molecular sieve and the active component is ferric chloride and aluminum chloride.

[0057] In some embodiments, the mass ratio of ferric chloride to aluminum chloride in the active components is (2-4):(1-3), including but not limited to 3:2, 2:1.5 or 3.5:2, etc., preferably 3:2.

[0058] In some embodiments, the zeolite molecular sieve includes, but is not limited to, at least one of MCM-22, SAPO-11, etc., with MCM-22 being preferred. When the zeolite molecular sieve MCM-22 is selected as the support, it has the following advantages compared to other types of zeolite molecular sieves: the elongated "V"-shaped pore structure of the MCM-22 catalyst is close to the spatial configuration of 2-methyl-6-propionylnaphthalene, which helps to improve the regioselectivity of acylation.

[0059] In the embodiments of this application, MCM-22 is selected as the support to simultaneously load the active components ferric chloride and aluminum chloride. The resulting supported molecular sieve catalyst is used for the synthesis of 2-methyl-6-acylnaphthalene and has the following advantages: it enhances the Lewis acidity of the MCM-22 catalyst, improves the activity of the reaction site, can increase the formation of acylnaphthalene at the 6-position, and can improve the overall conversion rate of 2-methylnaphthalene and the selectivity of the product.

[0060] Furthermore, compared to using MCM-22 as a support to load aluminum chloride or ferric chloride alone, choosing MCM-22 as a support to simultaneously load the active components ferric chloride and aluminum chloride has the following advantages: It allows Fe... 3+ Green sustainability and Al 3+ The high activity of these components, combined with AlCl3's ability to induce the formation of 6-acylnaphthalene and FeCl3's ability to reduce the formation of diacylnaphthalene byproducts, further enhances the reaction selectivity.

[0061] In some embodiments, the preparation method of the supported molecular sieve catalyst includes the following steps: (1) The carrier is pretreated to obtain a pretreated carrier; (2) The active component is dispersed in an organic solvent to obtain a dispersion; (3) The pretreated carrier is added to the dispersion, and then stirred and refluxed, filtered for the third time, dried, ground and calcined to obtain the supported molecular sieve catalyst.

[0062] In some embodiments, in step (1), the pretreatment temperature is 550-650°C, including but not limited to 575°C, 600°C or 625°C, preferably 600°C.

[0063] In some implementations, the pretreatment time in step (1) is 2-4 hours, including but not limited to 2.5 hours, 3 hours or 3.5 hours, preferably 3 hours.

[0064] In some embodiments, in step (2), the organic solvent includes, but is not limited to, at least one of chloroform (CHCl3), nitrobenzene, 1,2-dichloroethane, etc., preferably chloroform.

[0065] In some embodiments, step (2), which involves dispersing the active component in an organic solvent to obtain a dispersion, is performed in an inert gas atmosphere. Exemplary examples include, but are not limited to, at least one of nitrogen, helium, and argon, with nitrogen being preferred.

[0066] In some embodiments, in step (3), the temperature of the stirring reflux is 50.0-90.0℃, including but not limited to 60℃, 70℃ or 80℃.

[0067] In some implementations, the stirring and reflux time in step (3) is 1-3 hours, for example, 2 hours.

[0068] In the embodiments of this application, the above-mentioned stirring reflux refers to stirring to reflux the organic solvent.

[0069] In some embodiments, the calcination temperature in step (3) is 500-600°C, including but not limited to 525°C, 550°C or 575°C, preferably 550°C.

[0070] In some implementations, the roasting time in step (3) is 2-4 hours, including but not limited to 2.5 hours, 3 hours or 3.5 hours.

[0071] As an optional example, the composition of the 2-methyl-propionylnaphthalene mixture obtained in step S101 includes: 60.0-72.0 wt% 2-methyl-6-propionylnaphthalene, 22.5-35.0 wt% 2-methyl-7-propionylnaphthalene, and <3.0 wt% other 2-methyl-propionylnaphthalene isomers.

[0072] In the embodiments of this application, the above-mentioned supported molecular sieve catalyst is a green molecular sieve catalyst. 2-methylnaphthalene is used as raw material to synthesize a mixture of 2-methyl-propionylnaphthalene through heterogeneous catalysis of the green molecular sieve. This method is different from the traditional Lewis acid homogeneous catalyst synthesis method, which avoids the generation of a large amount of acidic wastewater by hydrolysis, and the catalyst can be recycled.

[0073] S102. The 2-methyl-propionylnaphthalene mixture obtained in step S101 is distilled to obtain crude 2-methyl-acylnaphthalene.

[0074] In some embodiments, the distillation is vacuum distillation.

[0075] In some embodiments, the distillation includes the following steps: 1) The 2-methyl-propionylnaphthalene mixture is subjected to a first distillation to remove unreacted propionic acid, propionic anhydride and a small amount of 2-methylnaphthalene; 2) The product after the first distillation is subjected to a second distillation to obtain crude 2-methyl-acylnaphthalene.

[0076] It should be noted that the crude 2-methyl-acylnaphthalene is the product after the first distillation and the fraction distilled off after the second distillation.

[0077] In some embodiments, the temperature of the first distillation is 115-117°C, and the pressure of the first distillation is 3.4-4.2 kPa.

[0078] For example, the pressure of the first distillation includes, but is not limited to, 3.6 kPa, 3.8 kPa or 4 kPa, preferably 3.8 kPa.

[0079] In some embodiments, the temperature of the second distillation is 185-188°C, and the pressure of the second distillation is 2.5-3.2 kPa.

[0080] For example, the pressure of the second distillation includes, but is not limited to, 2.7 kPa or 3 kPa, preferably 3 kPa.

[0081] In some embodiments, the crude 2-methyl-acylnaphthalene obtained by distilling the 2-methyl-propionylnaphthalene mixture includes 2-methyl-6-propionylnaphthalene, 2-methyl-7-propionylnaphthalene, and other MPN isomers, wherein: the purity of 2-methyl-6-propionylnaphthalene is greater than 60.0 wt%, the purity of 2-methyl-7-propionylnaphthalene is less than 35 wt%, and the purity of other MPN isomers is less than 3 wt%. Other MPN isomers include at least one of 2-methyl-1-propionylnaphthalene, 2-methyl-3-propionylnaphthalene, and 2-methyl-8-propionylnaphthalene.

[0082] S103. The crude 2-methyl-acylnaphthalene obtained in step S102 is melt-crystallized to obtain 2-methyl-6-propionylnaphthalene.

[0083] In some embodiments, the melt crystallization is carried out in a tubular melt crystallizer.

[0084] In the embodiments of this application, the tubular melt crystallizer itself is an existing device, and its specific structure will not be described in detail here.

[0085] In some embodiments, the melt crystallization includes the following steps: S1. Cool the crude 2-methyl-acylnaphthalene product to a first temperature at a first rate and hold it at that temperature for a first time. S2. The material after the first heat preservation is subjected to first filtration and separation of mother liquor, followed by sweating, second filtration and second heating.

[0086] In some embodiments, the sweating process includes: first heating to a second temperature at a second rate and then performing a second heat preservation.

[0087] In some embodiments, the first rate is 0.5-2℃ / h, for example, 1℃ / h or 1.5℃ / h. A first rate within this range yields a product with the required purity and yield; below 0.5℃ / h, the process is too time-consuming and energy-intensive; above 2℃ / h, the process results in increased impurity inclusion and reduced product purity.

[0088] In some embodiments, the first temperature is 38-42°C, such as 39°C, 40°C, or 41°C. Within this range, a product with the required purity and yield can be obtained; below 38°C, excessive crystallization and impurity inclusion occur, reducing product purity; above 42°C, low crystallization results in a lower final product yield.

[0089] In some embodiments, the first heat treatment time is 0.5-2 hours, such as 1 hour, 1.25 hours, or 1.5 hours. Within this range, a product with the required purity and yield can be obtained; less than 0.5 hours results in incomplete crystallization and a reduced yield; more than 2 hours leads to increased energy consumption without significant improvement in product purity and yield.

[0090] In some embodiments, the second rate is 0.5-3.5°C / h, for example, 1°C / h, 2°C / h, or 3°C / h. Within this range, a product with the required purity and yield can be obtained; below 0.5°C / h, the process is too time-consuming and energy-intensive; above 3.5°C / h, impurities migrate incompletely, sweat is not thoroughly expelled, and product purity decreases.

[0091] In some embodiments, the second temperature is 59-62°C, such as 60°C or 61°C. Within this range, products with the required purity and yield can be obtained; below 59°C, impurities increase and product purity decreases; above 62°C, energy consumption increases and yield decreases.

[0092] In some embodiments, the second holding time is 0.5-2 hours, such as 1 hour or 1.5 hours. Holding times within this range result in products with the required purity and yield; holding times below 0.5 hours result in incomplete impurity removal and reduced product purity; holding times above 2 hours lead to increased energy consumption, excessive melting of the crystal layer, and reduced yield.

[0093] In some embodiments, the termination temperature of the second heating is the temperature at which the crystal layer completely melts. This is done so that complete melting of the crystal layer facilitates product removal.

[0094] In the embodiments of this application, the temperature at which the crystal layer completely melts is in principle greater than the melting point of 2-methyl-6-propionylnaphthalene, which is 62°C, such as 70°C or 80°C.

[0095] In some embodiments, the melt crystallization further includes the steps of opening the bottom discharge valve of the melt crystallization system after the first heat preservation and closing the bottom discharge valve of the melt crystallization system after the second filtration.

[0096] In some implementations, the methods of the first filtration and the second filtration include, but are not limited to, vacuum filtration.

[0097] In some embodiments, the purity of the 2-methyl-6-propionylnaphthalene is above 99.0 wt%, including but not limited to above 99.1 wt%, above 99.2 wt%, above 99.3 wt%, above 99.4 wt%, above 99.5 wt%, above 99.6 wt%, above 99.7 wt%, above 99.8 wt%, or above 99.9 wt%.

[0098] The method for separating 2-methyl-6-propionylnaphthalene by melt crystallization according to the embodiments of this application can bring at least the following beneficial effects: 1. By combining distillation and melt crystallization, 2-methyl-acylnaphthalene is purified in one step through a systematic melt crystallization operation, resulting in 2-methyl-6-propionylnaphthalene with extremely high purity (above 99.0 wt%), which is difficult to achieve by solution recrystallization separation method. Moreover, the melt crystallization operation is simple and has low energy consumption.

[0099] 2. A mixture of 2-methyl-propionylnaphthalene is synthesized by heterogeneous catalysis using green molecular sieves as raw material. This method differs from the traditional Lewis acid homogeneous catalyst synthesis method, avoids the generation of large amounts of acidic wastewater from hydrolysis, and allows for catalyst recycling.

[0100] 3. Compared with the insulated suction funnel, the tubular static melting crystallizer is simple to operate, and the crystallization temperature, cooling rate and crystallization time are precisely controlled with high repeatability.

[0101] The following non-limiting embodiments further illustrate certain features of the present technology.

[0102] Example 1 The method for separating 2-methyl-6-propionylnaphthalene by melt crystallization in this embodiment includes the following steps: (1) Preparation of FeCl3 / AlCl3 / MCM-22 catalyst Pre-treat the MCM-22 molecular sieve in a muffle furnace at 600 °C for 3 h. Weigh 60 g of anhydrous ferric chloride and 40 g of anhydrous aluminum chloride into a 500 mL three-necked flask, then add 300 mL of CHCl3 (chloroform). Purge with nitrogen to purge air, and turn on the controller of the metal bath (also known as a dry thermostat or constant temperature metal bath instrument) to stir. After FeCl3 and AlCl3 have fully dissolved, add 50 g of the pre-treated MCM-22 zeolite molecular sieve (sieve-to-solvent ratio 1:6, where the sieve-to-solvent ratio is the numerical ratio of 50 g of catalyst to 300 mL of CHCl3). Heat to 62 °C and stir, allowing the solvent CHCl3 to reflux. After stirring for 1.5 h, heating was stopped until the three-necked flask cooled to room temperature (25 °C). The solid was washed with CHCl3, vacuum filtered, and placed in a vacuum drying oven at 50 °C overnight (16 h). After grinding, it was calcined in a muffle furnace at 550 °C for 3 h and cooled to room temperature (25 °C) to obtain the zeolite molecular sieve-supported FeCl3 / AlCl3 / MCM-22 catalyst.

[0103] (2) Synthesis of 2-methyl-6-acylnaphthalene Add 88.8 g (6.25 mol) of 2-methylnaphthalene, 162.7 g (12.5 mol) of propionic anhydride, and 35 g of the zeolite molecular sieve-supported FeCl3 / AlCl3 / MCM-22 catalyst prepared in step (1) to a 500 mL three-necked flask equipped with a drying tube, a condenser, and a thermometer. Under stirring conditions (stirring speed of 200 rpm), raise the temperature to 190 °C and react for 12 h. Then centrifuge to separate the solid catalyst (i.e., the zeolite molecular sieve-supported FeCl3 / AlCl3 / MCM-22 catalyst). The MCM-22 catalyst was separated from the liquid. The filtrate was distilled under reduced pressure at 115-117℃ / 3.8kPa to remove unreacted propionic acid, propionic anhydride, and a small amount of 2-methylnaphthalene. Then, crude 2-methyl-acylnaphthalene was distilled off at 185-188℃ / 2.7kPa. The crude 2-methyl-acylnaphthalene sample after reduced pressure distillation was analyzed by gas chromatography. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was 96.0% based on 2-methylnaphthalene. The selectivity of 2-methyl-6-propionylnaphthalene was 67.62%, the selectivity of 2-methyl-7-propionylnaphthalene was 28.91%, the formation (i.e., selectivity) of other MPN isomers was <1.47%, and the heavy component was 2.0%. The crude 2-methyl-acylnaphthalene after distillation had a purity of 69.0 wt% for 2-methyl-6-propionylnaphthalene and 29.5 wt% for 2-methyl-7-propionylnaphthalene, with other MPN isomers having a purity of <1.5 wt%. The other MPN isomers were 2-methyl-1-propionylnaphthalene (1,2-MPN), 2-methyl-3-propionylnaphthalene (2,3-MPN), and 2-methyl-8-propionylnaphthalene (2,8-MPN); the recombinant fraction consisted of diacylnaphthalene compounds (with higher melting and boiling points).

[0104] (3) Melt crystallization purification of 2-methyl-6-propylnaphthalene 180g of crude 2-methyl-6-propionylnaphthalene (temperature 51℃, 2-methyl-6-propionylnaphthalene content 69wt%) obtained by vacuum distillation in step (2) was added to a 200mL tubular melt crystallizer for crystallization. The cooling rate was 0.5℃ / h, the final cooling temperature was 42℃, and the final temperature was held for 0.5h. Then, the discharge valve at the bottom of the crystallizer was opened, and vacuum filtration was started to separate the mother liquor. Subsequently, sweating was carried out at a heating rate of 0.5℃ / h, the final sweating temperature was 62℃, and the final temperature was held for 0.5h. Then, vacuum filtration was started to separate the sweat. Finally, the discharge valve was closed, the temperature was raised to 80℃ to completely melt the crystal layer, and the discharge valve was opened to obtain the 2-methyl-6-propionylnaphthalene product (purity 99.4wt%, yield 47.1%).

[0105] Example 2 (compared to Example 1, the melting and crystallization conditions were changed) This embodiment is basically the same as embodiment 1, except that: Step (3) The process of molten crystallization purification of 2-methyl-6-propylnaphthalene is as follows: 180g of crude 2-methyl-6-propionylnaphthalene (51℃, 69wt% 2-methyl-6-propionylnaphthalene content) obtained by vacuum distillation in step (2) was added to a 200mL tubular melt crystallizer for crystallization. The cooling rate was 2℃ / h, and the final cooling temperature was 38℃. After holding at the final temperature for 2h, the discharge valve at the bottom of the crystallizer was opened, and vacuum filtration was started to separate the mother liquor. Subsequently, sweating was performed at a heating rate of 3.5℃ / h, and the final sweating temperature was 59℃. After holding at the final temperature for 0.5h, vacuum filtration was started to separate the sweat. Finally, the discharge valve was closed, and the temperature was raised to 80℃ to completely melt the crystal layer. The discharge valve was then opened to obtain the 2-methyl-6-propionylnaphthalene product (purity 99.1wt%, yield 50.6%).

[0106] Example 3 (Compared to Example 1, the melting and crystallization conditions were changed) This embodiment is basically the same as embodiment 1, except that: Step (3) The process of molten crystallization purification of 2-methyl-6-propylnaphthalene is as follows: 180g of crude 2-methyl-6-propionylnaphthalene (51℃, 69wt% 2-methyl-6-propionylnaphthalene content) obtained by vacuum distillation in step (2) was added to a 200mL tubular melt crystallizer for crystallization. The cooling rate was 0.5℃ / h, and the final cooling temperature was 38℃. After holding at the final temperature for 2h, the discharge valve at the bottom of the crystallizer was opened, and vacuum filtration was started to separate the mother liquor. Subsequently, sweating was performed at a heating rate of 0.5℃ / h, and the final sweating temperature was 59℃. After holding at the final temperature for 2h, vacuum filtration was started to separate the sweat. Finally, the discharge valve was closed, and the temperature was raised to 80℃ to completely melt the crystal layer. The discharge valve was then opened to obtain the 2-methyl-6-propionylnaphthalene product (purity 99.3wt%, yield 49.2%).

[0107] Example 4 (Compared to Example 1, the lower limit of the mass ratio of the catalyst active components ferric chloride and aluminum chloride is 2:3) This embodiment is basically the same as embodiment 1, except that: In step (1), replace “60g anhydrous ferric chloride and 40g anhydrous aluminum chloride” with “40g anhydrous ferric chloride and 60g anhydrous aluminum chloride”.

[0108] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was 96.5% based on 2-methylnaphthalene, the selectivity of 2-methyl-6-propionylnaphthalene was 67.8%, the selectivity of 2-methyl-7-propionylnaphthalene was 26.55%, the formation of other MPN isomers was <2.15%, and the heavy fraction was 3.5%. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 70.26 wt%, the purity of 2-methyl-7-propionylnaphthalene was 27.51 wt%, and the purity of other MPN isomers was <2.23 wt%.

[0109] In step (3), the crude 2-methyl-acylnaphthalene contains 70.26 wt% 2-methyl-6-propionylnaphthalene; the purity of the 2-methyl-6-propionylnaphthalene product is 99.1 wt%, and the yield is 43.8%.

[0110] Example 5 (Compared to Example 1, the upper limit of the mass ratio of the catalyst active components ferric chloride and aluminum chloride is 4:1) This embodiment is basically the same as embodiment 1, except that: In step (1), replace “60g anhydrous ferric chloride and 40g anhydrous aluminum chloride” with “80g anhydrous ferric chloride and 20g anhydrous aluminum chloride”.

[0111] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was 94.9% based on 2-methylnaphthalene, the selectivity of 2-methyl-6-propionylnaphthalene was 64.7%, the selectivity of 2-methyl-7-propionylnaphthalene was 31.4%, the formation of other MPN isomers was <2.85%, and the heavy component was 1.05%. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 65.39 wt%, the purity of 2-methyl-7-propionylnaphthalene was 31.73 wt%, and the purity of other MPN isomers was <2.88 wt%.

[0112] In step (3), the crude 2-methyl-acylnaphthalene contains 65.39 wt% 2-methyl-6-propionylnaphthalene; the purity of the 2-methyl-6-propionylnaphthalene product is 99.0 wt%, and the yield is 39.5%.

[0113] Example 6 (The reaction temperature was the lower limit of 180°C compared to Example 1) This embodiment is basically the same as embodiment 1, except that: In step (2), the temperature is increased to 180°C under stirring conditions (stirring speed of 200 rpm).

[0114] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was calculated based on 2-methylnaphthalene as 82.8%, the selectivity of 2-methyl-6-propionylnaphthalene was 62.52%, the selectivity of 2-methyl-7-propionylnaphthalene was 33.58%, the formation of other MPN isomers was <1.94%, and the heavy fraction was 1.96%. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 63.77 wt%, the purity of 2-methyl-7-propionylnaphthalene was 34.25 wt%, and the purity of other MPN isomers was <1.98 wt%.

[0115] In step (3), the crude 2-methyl-acylnaphthalene contains 63.77 wt% 2-methyl-6-propionylnaphthalene; the purity of the 2-methyl-6-propionylnaphthalene product is 99.1 wt%, and the yield is 42.8%.

[0116] Example 7 (The reaction temperature is the upper limit of 200°C compared to Example 1) This embodiment is basically the same as embodiment 1, except that: In step (2), the temperature is increased to 200°C under stirring conditions (stirring speed of 200 rpm).

[0117] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was 96.8% based on 2-methylnaphthalene, the selectivity of 2-methyl-6-propionylnaphthalene was 66.57%, the selectivity of 2-methyl-7-propionylnaphthalene was 26.33%, the formation of other MPN isomers was <2.1%, and the heavy component was 5.0%. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 70.07 wt%, the purity of 2-methyl-7-propionylnaphthalene was 27.72 wt%, and the purity of other MPN isomers was <2.21 wt%.

[0118] In step (3), the crude 2-methyl-6-propionyl naphthalene contains 70.07 wt% 2-methyl-6-propionyl naphthalene; the purity of the 2-methyl-6-propionyl naphthalene product is 99.2 wt%, and the yield is 43.2%.

[0119] Comparative Example 1 (compared to Example 1, step (3) is solution crystallization) This comparative example is basically the same as Example 1, except that: Step (3) involves the crystallization and purification of 2-methyl-6-propylnaphthalene from a solution. The specific procedure is as follows: 50g of crude 2-methyl-acylnaphthalene (2-methyl-6-propionylnaphthalene content of 69wt%) was finally purified by vacuum distillation in step (2) and 350g of methanol were added to a 500mL crystallizer. The mixture was heated to 40℃ until it was completely dissolved, and then the temperature was lowered at a rate of 10℃ / h. The final temperature was 5℃. After holding the final temperature for 0.5h, the mixture was filtered, and the filter cake was washed with methanol at 5℃ and dried to obtain the 2-methyl-6-propionylnaphthalene product (purity 97.3wt%, yield 50.2%).

[0120] Comparative Example 2 (The catalyst used was a conventional catalyst, compared to Example 1) This comparative example is basically the same as Example 1, except that: step (1) is not included, and in step (2), the “zeolite molecular sieve supported FeCl3 / AlCl3 / MCM-22 catalyst prepared in step (1)” is replaced with the existing catalyst H-Beta catalyst.

[0121] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was calculated based on 2-methylnaphthalene as 57.42%, the selectivity of 2-methyl-6-propionylnaphthalene was 55.2%, the selectivity of 2-methyl-7-propionylnaphthalene was 41.8%, the formation of other MPN isomers was <3.0%, and there were no heavy components. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 55.2 wt%, the purity of 2-methyl-7-propionylnaphthalene was 41.8 wt%, and the purity of other MPN isomers was <3.0 wt%.

[0122] In step (3), the crude 2-methyl-acylnaphthalene contains 55.2 wt% 2-methyl-6-propionylnaphthalene; the purity of the 2-methyl-6-propionylnaphthalene product is 98.5 wt%, and the yield is 28.3%.

[0123] Comparative Example 3 (Compared to Example 1, the catalyst does not contain the active component) This comparative example is basically the same as Example 1, except that: Step (1) is to pretreat the MCM-22 molecular sieve in a muffle furnace at 600 °C for 3 h.

[0124] In step (2), replace “the zeolite molecular sieve supported FeCl3 / AlCl3 / MCM-22 catalyst prepared in step (1)” with the catalyst prepared in step (1).

[0125] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was calculated based on 2-methylnaphthalene as 31.66%, the selectivity of 2-methyl-6-propionylnaphthalene was 23.13%, the selectivity of 2-methyl-7-propionylnaphthalene was 4.56%, the formation of other isomers was <72.31%, and there were no heavy components. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 23.13 wt%, the purity of 2-methyl-7-propionylnaphthalene was 4.56 wt%, and the purity of other MPN isomers was <72.31 wt%.

[0126] Since the purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene obtained by vacuum distillation in step (2) is too low to carry out the melt crystallization purification of 2,6-MPN, step (3) is not performed.

[0127] Comparative Example 4 (Compared to Example 1, the catalyst active component is only aluminum chloride) This comparative example is basically the same as Example 1, except that: In step (1), replace “60g anhydrous ferric chloride and 40g anhydrous aluminum chloride” with “100g anhydrous aluminum chloride”.

[0128] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was 95.2% based on 2-methylnaphthalene. The selectivity of 2-methyl-6-propionylnaphthalene was 67.257%, the selectivity of 2-methyl-7-propionylnaphthalene was 24.14%, the formation of other MPN isomers was <4%, and the heavy fraction was 4.6%. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 70.5 wt%, the purity of 2-methyl-7-propionylnaphthalene was 25.3 wt%, and the purity of other MPN isomers was <4.2 wt%.

[0129] In step (3), the crude 2-methyl-acylnaphthalene contains 70.5 wt% 2-methyl-6-propionylnaphthalene; the purity of the 2-methyl-6-propionylnaphthalene product is 98.1 wt%, and the yield is 41.2%.

[0130] Comparative Example 5 (compared to Example 1, the catalyst active component is only ferric chloride) This comparative example is basically the same as Example 1, except that: In step (1), replace “60g anhydrous ferric chloride and 40g anhydrous aluminum chloride” with “100g anhydrous ferric chloride”.

[0131] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was 93.8% based on 2-methylnaphthalene. The selectivity of 2-methyl-6-propionylnaphthalene was 60.67%, the selectivity of 2-methyl-7-propionylnaphthalene was 35.18%, and the formation of other MPN isomers was <4.15%, with no heavy components. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 60.67 wt%, the purity of 2-methyl-7-propionylnaphthalene was 35.18 wt%, and the purity of other MPN isomers was <4.15 wt%.

[0132] In step (3), the crude 2-methyl-acylnaphthalene contains 60.67 wt% 2-methyl-6-propionylnaphthalene; the purity of the 2-methyl-6-propionylnaphthalene product is 98.1 wt%, and the yield is 37.6%.

[0133] Comparative Example 6 (compared to Example 1, the catalyst support is a zeolite molecular sieve other than that described in this application) This comparative example is basically the same as Example 1, except that: In step (1), the MCM-22 molecular sieve is replaced with ZSM-5.

[0134] In step (2), the crude 2-methyl-acylnaphthalene sample after vacuum distillation was subjected to gas chromatography analysis. Due to the excess propionic anhydride, the conversion rate of 2-methylnaphthalene was calculated based on 2-methylnaphthalene as 28.2%, the selectivity of 2-methyl-6-propionylnaphthalene was 18.25%, the selectivity of 2-methyl-7-propionylnaphthalene was 5.75%, and the formation of other MPN isomers was <76.0%, with no heavy components. The purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene after distillation was 18.25 wt%, the purity of 2-methyl-7-propionylnaphthalene was 5.75 wt%, and the purity of other MPN isomers was <76.0 wt%.

[0135] Since the purity of 2-methyl-6-propionylnaphthalene in the crude 2-methyl-acylnaphthalene obtained by vacuum distillation in step (2) is too low to carry out the melt crystallization purification of 2,6-MPN, step (3) is not performed.

[0136] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0137] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0138] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for separating 2-methyl-6-propionylnaphthalene by melt crystallization, characterized in that, include: 2-methylnaphthalene and propionic anhydride were reacted in the presence of a catalyst to obtain a mixture of 2-methyl-propionylnaphthalene; The mixture of 2-methyl-propionylnaphthalene was distilled to obtain crude 2-methyl-acylnaphthalene. The crude 2-methyl-acylnaphthalene was melt-crystallized to obtain 2-methyl-6-propionylnaphthalene.

2. The method according to claim 1, characterized in that, The melting and crystallization are carried out in a tubular melting and crystallizing apparatus.

3. The method according to claim 1, characterized in that, The melt crystallization includes: The crude 2-methyl-acylnaphthalene product is cooled to a first temperature at a first rate and then subjected to a first heat preservation. The material after the first heat preservation is subjected to a first filtration and separation of mother liquor, followed by sweating, a second filtration, and a second heating; the sweating process includes: heating to a second temperature at a second rate and performing a second heat preservation.

4. The method according to claim 3, characterized in that, The first rate is 0.5-2℃ / h; And / or, the first temperature is 38-42°C; And / or, the first heat preservation time is 0.5-2 hours; And / or, the second rate is 0.5-3.5℃ / h; And / or, the second temperature is 59-62°C; And / or, the second heat preservation time is 0.5-2 hours; And / or, the termination temperature of the second heating is the temperature at which the crystal layer completely melts; And / or, the melt crystallization further includes the steps of opening the bottom discharge valve of the melt crystallization system after the first heat preservation and closing the bottom discharge valve of the melt crystallization system after the second filtration.

5. The method according to claim 1, characterized in that, The catalyst includes a supported molecular sieve catalyst; the supported molecular sieve catalyst includes a support and an active component, the support includes a zeolite molecular sieve, and the active component includes ferric chloride and aluminum chloride; And / or, the reaction is a heterogeneous catalytic synthesis reaction.

6. The method according to claim 5, characterized in that, In the active components, the mass ratio of ferric chloride to aluminum chloride is (2-4):(1-3). And / or, the zeolite molecular sieve includes at least one of MCM-22 and SAPO-11; And / or, the method for preparing the supported molecular sieve catalyst includes: The carrier is pretreated to obtain a pretreated carrier; The active component is dispersed in an organic solvent to obtain a dispersion; The pretreated carrier is added to the dispersion, followed by stirring and reflux, third filtration, drying, grinding, and calcination to obtain the supported molecular sieve catalyst.

7. The method according to claim 6, characterized in that, The pretreatment temperature is 550-650℃, and the pretreatment time is 2-4 hours; And / or, the organic solvent includes at least one of chloroform, nitrobenzene, and 1,2-dichloroethane; And / or, the temperature of the stirring reflux is 50.0-90.0℃, and the stirring reflux time is 1-3h; And / or, the calcination temperature is 500-600℃, and the calcination time is 2-4h.

8. The method according to claim 1, characterized in that, The molar ratio of 2-methylnaphthalene to propionic anhydride is 1:(1.5-2.5). And / or, the amount of catalyst added is 13.5-15.5% of the total mass of the 2-methylnaphthalene and propionic anhydride; And / or, the reaction temperature is 180-200°C, and the reaction time is 10-14 h.

9. The method according to claim 1, characterized in that, The purity of the 2-methyl-6-propionylnaphthalene is above 99.0 wt%; And / or, the distillation is vacuum distillation; And / or, the distillation includes: The 2-methyl-propionylnaphthalene mixture was subjected to a first distillation to remove unreacted propionic acid, propionic anhydride, and a small amount of 2-methylnaphthalene; The product after the first distillation was subjected to a second distillation to obtain crude 2-methyl-acylnaphthalene.

10. The method according to claim 9, characterized in that, The temperature of the first distillation is 115-117℃, and the pressure of the first distillation is 3.4-4.2 kPa; And / or, the temperature of the second distillation is 185-188°C, and the pressure of the second distillation is 2.5-3.2 kPa.

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