A method for preparing beta-methylnaphthalene from a methylnaphthalene-containing fraction based on solution homogeneous crystallization separation

Abstract

The application provides a method for preparing beta-methylnaphthalene from a methylnaphthalene-containing fraction based on solution homogenization crystallization separation, and comprises the following steps: pumping the methylnaphthalene-containing fraction into a fluidized bed reactor, performing primary cooling treatment, and performing ultrasonic treatment through an ultrasonic device arranged on the inner wall of the fluidized bed reactor, and then filtering after the crystallization treatment; re-heating the solid in the fluidized bed reactor, then performing secondary cooling treatment and ultrasonic treatment at the same time, and then filtering after the crystallization treatment; re-heating the solid in the fluidized bed reactor, then performing third cooling treatment, and performing ultrasonic treatment at the same time, and then filtering after the crystallization treatment, collecting the filter residue, and then drying to obtain high-purity beta-methylnaphthalene. The method combines the fluidized bed reactor with the ultrasonic treatment technology, and adopts step-by-step crystallization, so that impurities are effectively removed, high-purity beta-methylnaphthalene is obtained, and the yield of the product is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of β-methylnaphthalene purification, and particularly relates to a method for preparing β-methylnaphthalene based on solution homogeneous crystallization separation of methylnaphthalene fraction. BACKGROUND

[0002] Methylnaphthalene is an important organic compound and has a wide range of applications in industry, such as for preparing pesticides, medicines, dyes, plastics and the like. At present, the preparation methods of methylnaphthalene mainly include chemical synthesis method and separation and purification method. The chemical synthesis method usually needs multiple reactions, harsh reaction conditions, many side reactions, low yield and high cost. The separation and purification method is to separate methylnaphthalene and its isomers from carbon ten aromatic hydrocarbons through a series of distillation, fractional distillation, extraction and the like. β-methylnaphthalene in methylnaphthalene can be used for producing textile auxiliaries, lubricants and plant growth regulators, and more than 99% of high-purity β-methylnaphthalene is a raw material for synthesizing vitamin K drugs and feed additives. Extraction of β-methylnaphthalene from carbon ten crude aromatic hydrocarbons is a production method for producing β-methylnaphthalene in the industry at present. The purity of β-methylnaphthalene obtained by conventional purification from carbon ten aromatic hydrocarbons can reach about 98%, and there are generally α-methylnaphthalene and a small amount of quinoline and indole impurities, so it is necessary to further purify the β-methylnaphthalene to meet the market needs.

[0003] The separation and purification methods of beta-methylnaphthalene mainly include distillation, crystallization, column chromatography, ion exchange, etc. These methods can be selected and applied according to the physical and chemical properties of the substances and the relative differences with impurities. Among them, distillation is one of the most commonly used methods for separating and purifying beta-methylnaphthalene. The principle is to heat the mixture to above the boiling point of beta-methylnaphthalene, so that beta-methylnaphthalene evaporates in gaseous form, and then is cooled to liquid form by a condensing device, so as to separate it from other components. However, the distillation method can only preliminarily separate beta-methylnaphthalene from low-boiling-point components, and the separation effect for high-boiling-point components is not ideal. Column chromatography is a method of separating beta-methylnaphthalene from other components by using different polar solvents to elute beta-methylnaphthalene. The advantage of column chromatography is that it can realize continuous separation and purification of beta-methylnaphthalene, but it needs to find suitable eluent and elution conditions, and the separation effect of column chromatography is also affected by the packing. The ion exchange method is to use the difference in ion properties between beta-methylnaphthalene and other components, and to adsorb beta-methylnaphthalene in the mixture by ion exchange resin, and then to purify beta-methylnaphthalene by elution, concentration, drying and other steps. However, the ion exchange method needs a large amount of resin, and the regeneration and replacement of the resin also need to be considered. The crystallization method is to use the difference in solubility between beta-methylnaphthalene and other components, dissolve the mixture in a suitable solvent, and then precipitate beta-methylnaphthalene by cooling or evaporating the solvent, and then purify beta-methylnaphthalene by filtering and drying. The crystallization method has low cost and simple operation, and becomes the main method for separating and purifying beta-methylnaphthalene. The main problems in the current crystallization method are that the improper selection of crystallization conditions can easily affect the purity and yield of the product, and the crystallization efficiency of the product needs to be further improved. SUMMARY

[0004] The technical problem solved by the present application is to provide a method for preparing beta-methylnaphthalene based on solution homogeneous crystallization separation of methylnaphthalene fraction, which combines a fluidized bed reactor with ultrasonic treatment technology and uses step crystallization to effectively remove impurities and obtain high-purity beta-methylnaphthalene, and the yield of the product is also significantly improved.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] A method for preparing beta-methylnaphthalene based on solution homogeneous crystallization separation of methylnaphthalene fraction, comprising the following steps:

[0007] (1) Pump the methylnaphthalene fraction with a temperature of 70-80℃ into the fluidized bed reactor for primary cooling treatment, and perform ultrasonic treatment through the ultrasonic device arranged on the inner wall of the fluidized bed reactor at the same time, and then filter after the crystallization treatment;

[0008] (2) re-warming the solid in the fluidized bed reactor to 70-80℃, then performing secondary cooling treatment, and performing ultrasonic treatment through the ultrasonic device arranged on the inner wall of the fluidized bed reactor during the cooling treatment, and filtering after the crystallization treatment;

[0009] (3) re-warming the solid in the fluidized bed reactor to 70-80℃, then performing tertiary cooling treatment, and performing ultrasonic treatment through the ultrasonic device arranged on the inner wall of the fluidized bed reactor during the cooling treatment, and filtering after the crystallization treatment;

[0010] (4) collecting the filter residue obtained in step (3), then performing drying, and obtaining high-purity β-methylnaphthalene.

[0011] As a preferred embodiment of the above technical solution, in step (1), the temperature of the cooling treatment is 10-20℃, the time is 30-60min, and the power of the ultrasonic treatment is 200-400W.

[0012] As a preferred embodiment of the above technical solution, in step (2), the temperature of the cooling treatment is -18±2℃, the time is 30-60min, and the power of the ultrasonic treatment is 200-400W.

[0013] As a preferred embodiment of the above technical solution, in step (3), the temperature of the cooling treatment is -5~-10℃, the time is 30-60min, and the power of the ultrasonic treatment is 200-400W.

[0014] As a preferred embodiment of the above technical solution, the cooling rate of the primary cooling treatment, the secondary cooling treatment and the tertiary cooling treatment is 2-3℃ / min.

[0015] As a preferred embodiment of the above technical solution, the filtrate obtained by filtering in step (1), step (2) and step (3) is combined and re-entered into the fluidized bed reactor for primary cooling treatment, and the processes (2) and (3) are repeated.

[0016] Due to the adoption of the above technical solution, the present application has the following beneficial effects:

[0017] The present application adopts step-by-step crystallization method to separate and purify the methyl naphthalene fraction to obtain high-purity β-methyl naphthalene. In the specific operation, the present application adopts ultrasonic treatment to assist the cooling crystallization, and effectively adjusts the cooling rate and the ultrasonic power. If the ultrasonic power is too small, the cavitation effect of the ultrasonic wave is not enough to destroy the crystal lattice, thereby affecting the crystallization efficiency. When the ultrasonic power is too large, the energy released by the cavitation bubble when collapsing is too large, which may cause the destruction of the crystal structure, also affecting the crystallization efficiency. At the same time, the cooling rate also affects the crystallization effect. If the cooling rate is faster, the crystal growth rate is faster, and the crystal may be smaller, but it will also lead to uneven crystal and increase the crystal defects. The present application controls the cooling rate to be 2-3 ℃ / min.

[0018] The present application also adopts a fluidized bed reactor as a cooling crystallization container. The heat transfer coefficient between the bed layer and the inner immersed heat exchange surface of the fluidized bed reactor is very high, the total bed heat capacity is large, and the thermal stability is good. Therefore, the phenomenon of local overheating or incomplete local reaction can be avoided, the mass transfer and heat transfer efficiency is improved, and the crystallization efficiency is improved. The fluidized bed reactor can make the fine particles in the suspended state contact with the fluid, which is beneficial to the heterogeneous reaction, thereby promoting the crystallization and improving the crystallization efficiency.

[0019] The present application removes the impurities such as 1-methyl naphthalene, quinoline and indole in the methyl naphthalene fraction through ultrasonic treatment combined with fluidized bed reactor for multiple heating and cooling treatment, thereby obtaining high-purity 2-methyl naphthalene. The operation is simple and the cost is low. DETAILED DESCRIPTION

[0020] In order to better understand the present application, the present application is further illustrated by the following examples, which are only used to explain the present application and will not constitute any limitation on the present application.

[0021] The β-methyl naphthalene fraction content in the methyl naphthalene fraction in the following examples and comparative examples is 65wt%.

[0022] Example 1

[0023] (1) 50kg of the methyl naphthalene fraction with a temperature of 80℃ is pumped into the fluidized bed reactor, and cooled to 15℃ at a cooling rate of 2℃ / min, while the ultrasonic device arranged on the inner wall of the fluidized bed reactor is used for ultrasonic treatment at 250W for 60min, and then filtered after the crystallization treatment;

[0024] (2) The solid in the fluidized bed reactor is re-heated to 80℃, and then cooled to -18±2℃ at a cooling rate of 2℃ / min, while the ultrasonic device arranged on the inner wall of the fluidized bed reactor is used for ultrasonic treatment at 250W for 60min, and then filtered after the crystallization treatment;

[0025] (3) The solid in the fluidized bed reactor was re-heated to 80°C, then cooled to -5°C at a cooling rate of 2°C / min, and ultrasonic treatment was performed at 250W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0026] (4) The filter residue obtained in step (3) was collected and then dried to obtain 22.77 kg of high-purity β-methylnaphthalene, and the product yield was 70.01%.

[0027] Example 2

[0028] (1) The methylnaphthalene-containing fraction at a temperature of 80°C was pumped into the fluidized bed reactor, cooled to 18°C at a cooling rate of 3°C / min, and ultrasonic treatment was performed at 250W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor, and then filtered after the crystallization process;

[0029] (2) The solid in the fluidized bed reactor was re-heated to 80°C, then cooled to -18±2°C at a cooling rate of 3°C / min, and ultrasonic treatment was performed at 250W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0030] (3) The solid in the fluidized bed reactor was re-heated to 80°C, then cooled to -10°C at a cooling rate of 3°C / min, and ultrasonic treatment was performed at 250W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0031] (4) The filter residue obtained in step (3) was collected and then dried to obtain 23.15 kg of high-purity β-methylnaphthalene, and the product yield was 71.23%.

[0032] Example 3

[0033] (1) The methylnaphthalene-containing fraction at a temperature of 80°C was pumped into the fluidized bed reactor, cooled to 15°C at a cooling rate of 2.5°C / min, and ultrasonic treatment was performed at 300W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor, and then filtered after the crystallization process;

[0034] (2) The solid in the fluidized bed reactor was re-heated to 80°C, then cooled to -18±2°C at a cooling rate of 2.5°C / min, and ultrasonic treatment was performed at 300W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0035] (3) The solid in the fluidized bed reactor was re-heated to 80°C, then cooled to -10°C at a cooling rate of 2.5°C / min, and ultrasonic treatment was performed at 300W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0036] (4) The filter residue obtained in step (3) was collected and dried to obtain 23.63 kg of high-purity β-methylnaphthalene, and the product yield was 72.71%.

[0037] Example 4

[0038] (1) The methyl naphthalene-containing fraction at a temperature of 80°C was pumped into the fluidized bed reactor, cooled to 15°C at a cooling rate of 3°C / min, and ultrasonic treatment was performed at 300W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0039] (2) The solid in the fluidized bed reactor was re-heated to 80°C, then cooled to -18±2°C at a cooling rate of 3°C / min, and ultrasonic treatment was performed at 300W for 30-60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0040] (3) The solid in the fluidized bed reactor was re-heated to 80°C, then cooled to -10°C at a cooling rate of 3°C / min, and ultrasonic treatment was performed at 300W for 60 min by the ultrasonic device set on the inner wall of the fluidized bed reactor during the cooling process, and then filtered after the crystallization process;

[0041] (4) The filter residue obtained in step (3) was collected and dried to obtain 25.01 kg of high-purity β-methylnaphthalene; the product yield was 76.95%.

[0042] (5) The filtrate obtained by filtering in steps (1), (2) and (3) was collected and combined and re-entered into the fluidized bed reactor for one cooling process, and the processes (2), (3) were repeated.

[0043] Comparative Example 1

[0044] The ultrasonic power was 100W in the one cooling process, the two cooling processes and the three cooling processes, and other conditions were the same as in Example 4, and 20.89 kg of β-methylnaphthalene was obtained, and the product yield was 64.28%.

[0045] Comparative Example 2

[0046] The ultrasonic power was 800W in the one cooling process, the two cooling processes and the three cooling processes, and other conditions were the same as in Example 4, and 21.05 kg of β-methylnaphthalene was obtained, and the product yield was 64.77%.

[0047] Comparative Example 3

[0048] The container used in the primary cooling treatment, the secondary cooling treatment and the tertiary cooling treatment was a common stirred reactor, and other conditions were the same as those in Example 4, and 20.13 kg of β-methylnaphthalene was obtained, and the product yield was 61.94%.

[0049] Comparative Example 4

[0050] The ultrasonic treatment was not used in the primary cooling treatment, the secondary cooling treatment and the tertiary cooling treatment, and other conditions were the same as those in Example 4, and 19.25 kg of β-methylnaphthalene was obtained, and the product yield was 59.23%.

[0051] The purity of the β-methylnaphthalene obtained in the above examples and comparative examples was tested, and the purity of the β-methylnaphthalene obtained in Examples 1-4 and Comparative Examples 1, 3-4 was all above 99%, and the purity of the β-methylnaphthalene obtained in Comparative Example 2 was only 97.9%, which was mainly because the interaction between the impurities and the precipitated crystals, including adsorption and inclusion, was increased when the ultrasonic power was high, thereby affecting the yield and purity of the product. Therefore, the yield of the product in Comparative Example 2 was also not as high as that in Example 4. The yield of the product in Comparative Examples 1 and 4 was also not very high compared with that in Example 4 when the ultrasonic power was too low or the ultrasonic treatment was not used, which was mainly because the cavitation effect of the ultrasonic wave was not enough to destroy the crystal lattice, thereby affecting the crystallization efficiency. The use of the fluidized bed reactor to perform the crystallization treatment in Comparative Example 3 and Example 4 could obviously improve the yield of the product, which was mainly because the heat transfer effect of the fluidized bed reactor was good, which was conducive to the heterogeneous reaction, thereby promoting the crystallization and improving the crystallization efficiency.

[0052] In addition, it should be understood that, after reading the content taught by the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope defined by the claims attached to the present application.

Claims

1. A method for preparing β-methylnaphthalene based on solution homogeneous crystallization separation of methylnaphthalene-containing fractions, characterized in that, Includes the following steps: (1) The methylnaphthalene-containing fraction at a temperature of 70-80℃ is pumped into a fluidized bed reactor for a cooling treatment. At the same time as the cooling treatment, ultrasonic crystallization is performed by an ultrasonic device installed on the inner wall of the fluidized bed reactor. After crystallization, the fraction is filtered. The cooling temperature is 10-20℃ and the time is 30-60 min. The ultrasonic power is 200-400 W. (2) The solid in the fluidized bed reactor is reheated to 70-80℃, and then subjected to a second cooling treatment. At the same time as the cooling treatment, ultrasonic crystallization treatment is performed by an ultrasonic device set on the inner wall of the fluidized bed reactor. After the crystallization treatment, the solid is filtered. The cooling temperature is -18±2℃, the time is 30-60min, and the ultrasonic power is 200-400W. (3) The solid in the fluidized bed reactor is reheated to 70-80℃, and then cooled three times. At the same time as the cooling process, ultrasonic crystallization is performed by an ultrasonic device set on the inner wall of the fluidized bed reactor. After the crystallization process, the solid is filtered. The temperature of the cooling process is -5 to -10℃, the time is 30-60 min, and the power of the ultrasonic process is 200-400W. (4) Collect the filter residue obtained in step (3) and then dry it to obtain high-purity β-methylnaphthalene.

2. The method for preparing β-methylnaphthalene based on solution homogeneous crystallization separation of methylnaphthalene-containing fractions according to claim 1, characterized in that, The cooling rate for the first, second, and third cooling treatments was 2-3℃ / min.

3. The method for preparing β-methylnaphthalene based on solution homogeneous crystallization separation of methylnaphthalene-containing fractions according to claim 1, characterized in that, The filtrates obtained from filtration in steps (1), (2) and (3) are combined and re-entered into the fluidized bed reactor for a cooling process, and processes (2) and (3) are repeated.