CN115716783A - Method for preparing azelaic acid through microwave-assisted autocatalytic hydrolysis of monomethyl azelate - Google Patents
Method for preparing azelaic acid through microwave-assisted autocatalytic hydrolysis of monomethyl azelate Download PDFInfo
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- CN115716783A CN115716783A CN202211488586.1A CN202211488586A CN115716783A CN 115716783 A CN115716783 A CN 115716783A CN 202211488586 A CN202211488586 A CN 202211488586A CN 115716783 A CN115716783 A CN 115716783A
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Abstract
The invention discloses a method for preparing azelaic acid by microwave-assisted autocatalytic hydrolysis of monomethyl azelate, which comprises the steps of taking monomethyl azelate which is a downstream product of grease as a raw material, mixing the raw material with water in a certain proportion, carrying out autocatalytic hydrolysis reaction in a microwave reactor, carrying out heat preservation and layering, cooling and crystallization, carrying out vacuum filtration and vacuum drying to obtain a azelaic acid product, wherein the purity of the azelaic acid product is over 99 percent. The method skillfully utilizes microwave to strengthen the carboxyl hydrogen ionization of the reactant azelaic acid monomethyl ester and the product azelaic acid, improves the concentration of the hydrogen ions of the system, and accelerates the ester hydrolysis reaction of the azelaic acid monomethyl ester; meanwhile, microwave is utilized to strengthen oil-water two-phase mixing and mass transfer, thereby accelerating the vaporization of the byproduct methanol, promoting the forward progress of the hydrolysis reaction, accelerating the hydrolysis reaction rate and ensuring that the conversion rate of the monomethyl azelate reaches more than 99 percent. The method has the advantages of simple process, green and renewable raw materials, no need of a catalyst, greenness and high efficiency.
Description
Technical Field
The invention belongs to the technical field of development of downstream products of biodiesel, and particularly relates to a method for preparing azelaic acid through microwave-assisted autocatalytic hydrolysis of monomethyl azelate.
Background
Azelaic acid, also known as azelaic acid, is a type of medium and long chain dibasic acid and has a very wide industrial application. In the industrial field, azelaic acid is mainly used for synthesizing dioctyl azelate and isobutyl azelate plasticizer. In the field of medicine, azelaic acid is added to plasters for the treatment of skin diseases with its antibacterial activity, and is also used for the production of related cosmetics and the like with an effect of inhibiting pigment abnormality. Besides, the azelaic acid can be used for producing lubricating oil, spice, emulsifier, macromolecular nylon 69, capacitor, flame retardant, flocculant and the like, and has high use value.
At present, oleic acid is mainly used as a raw material for preparing azelaic acid by an ozone oxidation cracking method in industry, and then the azelaic acid is purified by reduced pressure distillation, solvent extraction and crystallization. The cracking product of azelaic acid prepared from oleic acid contains a large amount of reaction byproducts of alcohol, aldehyde and acid and saturated fatty acid which does not participate in the reaction, and intermolecular carboxyl and hydroxyl have association of hydrogen bonds, so that the separation and purification process is complex and the production cost is high. CN 108164416B attempts to prepare monomethyl azelate by ozone oxidative cracking using purified methyl oleate as a raw material, and the crude monomethyl azelate can be rectified to obtain high-purity monomethyl azelate. The azelaic acid monomethyl ester can obtain a high-purity azelaic acid product through hydrolysis reaction in an acid environment, the conversion rate of the hydrolysis reaction can reach 99% under the condition of taking sulfuric acid and other strong acids as catalysts, which shows that the preparation of azelaic acid through hydrolysis of the azelaic acid monomethyl ester has technical feasibility, but the problem of a large amount of acid waste water is generated, the sulfur content of the product is high, the subsequent separation process is complex, the content of hydrogen ions ionized from the azelaic acid monomethyl ester in a hydrolysis system without the catalyst is low, and the conversion efficiency of the hydrolysis reaction is low under the catalytic action of hydronium ions.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims at providing a method for preparing azelaic acid by microwave-assisted autocatalytic hydrolysis of monomethyl azelate, which is particularly suitable for a way for preparing azelaic acid from downstream products of grease.
The technical scheme adopted by the invention is as follows:
the method for preparing azelaic acid by microwave-assisted self-catalyzed hydrolysis of monomethyl azelate comprises the following steps: taking an oil downstream product, namely, monomethyl azelate, as a raw material, mixing the raw material with deionized water, transferring a reaction solution into a microwave reactor to react under microwave radiation, and subjecting the raw material of monomethyl azelate and a subsequently generated product of azelaic acid to dipole polarization and ion mass transfer under the action of microwave so as to dissociate hydrogen ions, thereby realizing the rapid autocatalytic hydrolysis reaction of monomethyl azelate, continuously evaporating methanol vapor in the reaction process, condensing and collecting the methanol vapor; after the reaction is finished, the reaction solution is subjected to heat preservation layering, cooling crystallization, reduced pressure suction filtration and vacuum drying in sequence to obtain the product azelaic acid.
Further, the mass ratio of the raw material monomethyl azelate to the deionized water is 1:8 to 16, preferably 1:10 to 12.
Further, the hydrolysis reaction temperature is 90 to 99 ℃, preferably 95 to 99 ℃.
Further, the hydrolysis reaction time is 1 to 6h, preferably 2.5 to 4h.
Further, the temperature of the cooling crystallization is 10-30 ℃, preferably 10-20 ℃.
Further, the heating power of the microwave is 200W-600W, preferably 300W-500W.
The preparation method of the invention has the following advantages and beneficial effects:
(1) The carboxyl of the raw material monomethyl azelate has stronger polarity, and dipole polarization and ion mass transfer are easy to occur in a microwave field, so that the hydrogen ion concentration of a system is improved, the concentration of hydronium ions is increased, and the autocatalysis effect on hydrolysis reaction is enhanced; meanwhile, as the reaction proceeds, two carboxyl groups of the product azelaic acid further generate dipole polarization and ion mass transfer under the action of microwaves, more hydrogen ions are dissociated, and the concentration of hydronium ions is increased, so that the rapid autocatalytic hydrolysis reaction of monomethyl azelate is realized.
(2) In the invention, the raw material monomethyl azelate molecules and water molecules move and collide at high speed under the action of a microwave field, so that the mass transfer of oil and water phases is enhanced, and the hydrolysis reaction rate is greatly accelerated; on the other hand, the microwave heating is helpful for the vaporization of the byproduct methanol, changes the phase equilibrium, promotes the hydrolysis reaction to proceed in the forward direction, and improves the conversion rate of the monomethyl azelate (methanol vapor distilled out in the reaction carries a large amount of moisture, and the moisture can be condensed and then returned to the microwave reactor, and then the uncondensed methanol is condensed and collected).
(3) The method does not need to add acid catalysts such as sulfuric acid and the like, avoids the problems of equipment corrosion, acid wastewater pollution and the like, and has the advantages of simple process flow, greenness, high efficiency and low energy consumption.
Drawings
FIG. 1 is a schematic flow diagram of a method for preparing azelaic acid by microwave-assisted autocatalytic hydrolysis of monomethyl azelate according to the present invention.
Detailed Description
The invention is further illustrated with reference to the following specific examples, without limiting the scope of the invention thereto.
The flow chart of the method for preparing azelaic acid in the embodiment of the invention is shown in figure 1, methanol steam is continuously distilled off in the reaction, and moisture carried by the steam is condensed and returned to the reactor.
Example 1
Taking 12.20g of raw material of monomethyl azelate with the mass fraction of 99.5%, mixing the raw material of monomethyl azelate with water, placing the mixture in a microwave reactor, and under the conditions of microwave power of 300W and hydrolysis temperature of 95 ℃, the mass ratio of monomethyl azelate to deionized water is 1:12.3, the reaction is carried out in a microwave reactor for 4.0 h, the conversion rate of the monomethyl azelate can reach more than 99 percent, and the conversion rate comparison condition is shown in Table 1. And after the reaction is finished, placing the mixture in a heat-preservation separating funnel for standing for 1h, placing the lower-layer water phase at 15 ℃ for cooling crystallization, and obtaining 10.71g of azelaic acid after reduced pressure suction filtration and vacuum drying.
The purity and yield of azelaic acid were determined by HG/T4481-2012 industrial azelaic acid standard, and in this example, the purity of the final azelaic acid was 99.57% and the yield of azelaic acid was 94.80%. The results of comparing the azelaic acid product obtained with commercially available azelaic acid products are shown in Table 2.
Example 2
Taking 12.22g of raw monomethyl azelate with the mass fraction of 99.5%, mixing the raw monomethyl azelate with water, placing the mixture in a microwave reactor, and under the conditions of the microwave power of 400W and the hydrolysis temperature of 99 ℃, ensuring that the mass ratio of the monomethyl azelate to the deionized water is 1:13.6, the reaction is carried out in a microwave reactor for 3.0 h, the conversion rate of the monomethyl azelate can reach more than 99 percent, and the conversion rate comparison condition is shown in Table 1. And after the reaction is finished, placing the mixture into a heat-preservation separating funnel, standing the mixture for 1h, placing the lower-layer water phase at 20 ℃ for cooling crystallization, and obtaining 10.88 g of the product azelaic acid after decompression, suction filtration and vacuum drying.
The yield and purity of azelaic acid was determined by HG/T4481-2012 industry using standards for azelaic acid. The purity of the azelaic acid finally obtained in this example was 99.52%, and the yield of azelaic acid was 96.15%. The results of comparing the azelaic acid product obtained with commercially available azelaic acid products are shown in Table 2.
Example 3
Taking 12.18g of raw monomethyl azelate with the mass fraction of 99.5%, mixing the raw monomethyl azelate with water, placing the mixture in a microwave reactor, and under the conditions of the microwave power of 500W and the hydrolysis temperature of 99 ℃, ensuring that the mass ratio of the monomethyl azelate to the deionized water is 1:13.7, the reaction time is 2.5 h in the microwave reactor, the conversion rate of the monomethyl azelate can reach more than 99 percent, and the comparison condition of the conversion rate is shown in the table 1. And after the reaction is finished, placing the mixture in a heat-preservation separating funnel for standing for 1h, placing the lower-layer water phase at 15 ℃ for cooling crystallization, and obtaining 10.78g of azelaic acid after reduced pressure suction filtration and vacuum drying.
The yield and purity of azelaic acid was determined by HG/T4481-2012 industry using standards for azelaic acid. The purity of azelaic acid finally obtained in this example was 99.53%, and the yield of azelaic acid was 95.58%. The results of comparing the obtained azelaic acid product with commercially available azelaic acid products are shown in Table 2.
Example 4
Taking 12.33 g of raw monomethyl azelate with the mass fraction of 99.5%, mixing the raw monomethyl azelate with water, placing the mixture in a microwave reactor, and under the conditions of the microwave power of 500W and the hydrolysis temperature of 95 ℃, ensuring that the mass ratio of the monomethyl azelate to the deionized water is 1:11.2, the conversion rate of the monomethyl azelate can reach more than 99 percent after the reaction is carried out in a microwave reactor for 3.0 hours, and the comparison condition of the conversion rate is shown in the table 1. And after the reaction is finished, placing the mixture in a heat-preservation separating funnel for standing for 1h, placing the lower-layer water phase at 13 ℃ for cooling crystallization, and obtaining 10.74 g of azelaic acid after reduced pressure suction filtration and vacuum drying.
The yield and purity of azelaic acid was determined by HG/T4481-2012 industry using standards for azelaic acid. The purity of azelaic acid finally obtained in this example was 99.48%, and the yield of azelaic acid was 94.07%. The results of comparing the obtained azelaic acid product with commercially available azelaic acid products are shown in Table 2.
Comparative example 1
Taking 12.21 g of a monomethyl azelate raw material with the mass fraction of 99.5%, mixing the monomethyl azelate raw material with water, placing the mixture in a reactor, and heating the reactor in a conventional oil bath at the hydrolysis temperature of 98 ℃ in a mass ratio of the monomethyl azelate to deionized water of 1:12.2, the reaction was heated in an oil bath for 6.0 h, and the conversion of monomethyl azelate was about 5%, as compared to Table 1. And after the reaction is finished, placing the mixture into a heat-preservation separating funnel, standing the mixture for 1h, placing the lower-layer water phase at 15 ℃ for cooling crystallization, and obtaining 0.56 g of azelaic acid after decompression, suction filtration and vacuum drying.
The yield and purity of azelaic acid was determined by HG/T4481-2012 industry using criteria for azelaic acid. The purity of azelaic acid finally obtained in this example was 92.1%, and the yield of azelaic acid was 4.56%. The results of comparing the obtained azelaic acid product with commercially available azelaic acid products are shown in Table 2.
As can be seen from table 1: comparative example 1 adopts the mode of conventional oil bath heating, and azelaic acid monomethyl ester raw materials are rarely hydrolyzed in water under the environment without acid addition, compared with the prior art that the conversion rate of the hydrolysis reaction can reach 99% under the condition of taking acid as a catalyst, which shows that the preparation of azelaic acid by hydrolyzing the azelaic acid monomethyl ester under the acid environment has technical feasibility.
However, in the embodiments 1 to 4 of the present invention, a microwave reaction mode is adopted, an additional acid catalyst is not required, the conversion rate of the hydrolysis reaction of the monomethyl azelate can reach more than 99%, the microwave reaction of the present invention promotes dissociation of more hydrogen ions, and the concentration of the hydronium ions is increased, so that the rapid autocatalytic hydrolysis reaction of the monomethyl azelate is realized, and unexpected technical effects are obtained.
The statements in this specification merely set forth a list of implementations of the inventive concept and the scope of the present invention should not be construed as limited to the particular forms set forth in the examples.
Claims (6)
1. A method for preparing azelaic acid by microwave-assisted self-catalyzed hydrolysis of monomethyl azelate is characterized by comprising the following steps: mixing a downstream product of grease, namely, monomethyl azelate, serving as a raw material with deionized water, transferring a reaction liquid into a microwave reactor to react under microwave radiation, and under the action of microwaves, enabling the raw material of monomethyl azelate and a subsequently generated azelaic acid product to generate dipole polarization and ion mass transfer so as to dissociate hydrogen ions, thereby realizing the rapid autocatalytic hydrolysis reaction of monomethyl azelate, and continuously evaporating methanol vapor and condensing and collecting the methanol vapor in the reaction process; after the reaction is finished, the reaction solution is subjected to heat preservation layering, cooling crystallization, reduced pressure suction filtration and vacuum drying in sequence to obtain the product azelaic acid.
2. The method for preparing azelaic acid through microwave-assisted autocatalytic hydrolysis of monomethyl azelate as in claim 1, wherein the mass ratio of the raw material monomethyl azelate to deionized water is 1:8 to 16, preferably 1:10 to 12.
3. The method for preparing azelaic acid through microwave-assisted self-catalyzed hydrolysis of monomethyl azelate as claimed in claim 1, wherein the hydrolysis reaction temperature is 90 to 99 ℃, preferably 95 to 99 ℃.
4. The method for preparing azelaic acid through microwave-assisted self-catalyzed hydrolysis of monomethyl azelate as claimed in claim 1, wherein the hydrolysis reaction time is 1 to 6h, preferably 2.5 to 4h.
5. A process for the preparation of azelaic acid by the autocatalytic hydrolysis of monomethyl azelate assisted by microwaves as claimed in claim 1, characterized in that the temperature of the cooling crystallization is 10-30 ℃, preferably 10-20 ℃.
6. A process for the preparation of azelaic acid by microwave assisted autocatalytic hydrolysis of monomethyl azelate according to claim 1 wherein the microwave heating power is from 200W to 600W, preferably from 300W to 500W.
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