KR20220061745A - Method for vaporizing lactic acid, and method for preparing acrylic acid from lactic acid - Google Patents

Abstract

The present specification relates to a lactic acid vaporization method, a lactic acid vaporization apparatus, and a method for preparing acrylic acid from lactic acid. According to the lactic acid vaporization method and apparatus of the present invention, the content of lactic acid oligomers can be reduced and the content of lactic acid single molecules can be increased within a short period of time. The lactic acid vaporization method includes a step of mixing and spraying liquid phased first stream including a lactic acid aqueous solution and gas phased second stream including vapor; a step of vaporizing the lactic acid aqueous solution; and a step of obtaining gas phased third stream including lactic acid single molecules.

Description

Lactic acid vaporization method, and acrylic acid production method

The present specification relates to a method for vaporizing lactic acid, and a method for preparing acrylic acid from lactic acid.

Lactic acid, also called lactic acid or lactic acid, is an organic acid with a relatively simple structure that contains both a hydroxy group and a carboxyl group in a molecule.

Lactic acid is traditionally mainly produced naturally during the fermentation process of lactose or glucose, and has played a role in improving the flavor of fermented foods. It has been used variously in the cosmetic field, such as a skin whitening agent, or in the medical field, such as an intravenous solution, a dialysis solution, and a calcium agent.

Recently, lactic acid polymer and polylactide are biodegradable, so interest is increasing as an eco-friendly alternative polymer that can replace plastics that are not naturally decomposed, such as polyolefin, polystyrene, and polyester manufactured from petroleum. It is also receiving high attention as a precursor of acrylic acid, which is considered to be very important.

Lactic acid can be mainly produced by microbial fermentation or chemical synthesis. Recently, starch-based biomass such as corn, sugar-based biomass such as sugar cane, or cellulose-based biomass obtained from woody or herbaceous plants, etc., Methods for producing lactic acid using biomass resources as raw materials are being studied.

Lactic acid obtained in this way is usually concentrated and stored at a high concentration during storage or distribution after production. Alternatively, water molecules are removed to form an oligomer in the form of dehydration condensation.

A large amount of lactic acid is lost by such dimerization or oligomerization, but the oligomerized lactic acid increases the amount of by-products generated in the chemical reaction using lactic acid and forms coking in the reaction process, which greatly reduces the efficiency of the reaction. There is this.

Therefore, it is necessary to reduce the content of lactic acid oligomers when using concentrated and stored lactic acid as lactic acid itself or adding it to other chemical reactions. , and temperature are known to be involved, and since the equilibrium transfer rate is very slow, a pretreatment method for using concentrated lactic acid, that is, a method for reducing the content of lactic acid oligomers in the feed and increasing the content of lactate single molecules. Interest is growing.

An object of the present specification is to provide a lactic acid vaporization method capable of reducing the content of lactic acid oligomers and increasing the content of single lactic acid molecules within a short time.

In addition, the present specification is to provide a method for producing acrylic acid from the vaporized lactic acid.

Herein, the mixing spraying of a first stream of a liquid phase containing an aqueous lactic acid solution and a second stream of a gas phase containing water vapor;

vaporizing the aqueous lactic acid solution through heat exchange between the first stream and the second stream; and

obtaining a third stream of gaseous phase comprising short molecules of lactic acid;

A method for vaporizing lactic acid is provided.

According to one embodiment of the invention, the lactic acid aqueous solution included in the first stream has a lactic acid concentration of about 40 to about 99 wt%, about 45 wt% or more, or about 50 wt% or more, or about 60 wt% or more, or about 70 wt% or more, or about 75 wt% or more, and about 99 wt% or less, about 95 wt% or less, or about 90 wt% or less, or about 85 wt% or less, and may be highly concentrated. .

And, the concentration of the multimer in the aqueous lactic acid solution included in the first stream, that is, the concentration of the lactic acid dimer or trimer or more of the lactic acid oligomer is about 2 to about 55 wt%, or about 2 wt% or more, or about 5 % or more, or about 7 wt% or more, or about 8 wt% or more, about 55 wt% or less, or about 40 wt% or less, or about 20 wt% or less, the content of the multimer may be relatively high .

According to another embodiment of the invention, the temperature of the first stream may be about 10 to about 300 °C, preferably about 10 °C or more, or about 15 °C or more, or about 50 °C or more, and about 300 °C or less, or about 250° C. or less, or about 200° C. or less.

And, the temperature of the second stream may be from about 200 to about 600 °C, preferably from about 250 °C or more, or about 300 °C or more, or about 350 °C or more, or about 400 °C or more, and about 600 °C or less, or about 550 °C or less, or about 530 °C or less.

In this case, the temperature difference between the second stream and the first stream may be about 200 °C or more, or about 250 °C or more, and it may be preferably about 500 °C or less, or about 450 °C or less.

According to another embodiment of the invention, the first stream may be sprayed at a flow rate of 0.05 g/min to 1.5 g/min, and the lower limit thereof is about 0.05 g/min or more, or about 0.1 g/min or more. , or about 0.15 g/min or more, or about 0.18 g/min or more, and the upper limit thereof is preferably about 1.5 g/min or less, or about 1.0 g/min or less, or about 0.8 g/min or less. can do.

And, the second stream may be sprayed at a flow rate of 0.1 g/min to 4.0 g/min, and the lower limit thereof is about 0.1 g/min or more, or about 0.2 g/min or more, or about 0.3 g/min. or more, and the upper limit thereof may preferably be about 4.0 g/min or less, or about 3.0 g/min or less, or about 2.0 g/min or less.

In this case, in the mixing spraying step, the first stream flow rate: the second stream flow rate may be preferably about 1: 1.5 to about 1: 5.

On the other hand, this specification,

a feed supply unit for supplying a first stream comprising an aqueous lactic acid solution;

a water vapor supply unit for supplying a second stream comprising water vapor;

a spray unit in which the lactic acid aqueous solution transferred from the feed supply unit and the water vapor transferred from the water vapor supply unit are mixed and sprayed;

After the mixed spray, the lactic acid aqueous solution is vaporized, the vaporization reaction unit; and an harvesting portion for obtaining a third stream comprising vaporized lactic acid molecules;

A device for vaporizing lactic acid is provided.

In this case, the spray unit may include a lactic acid nozzle to which the aqueous lactic acid solution is sprayed and a steam nozzle to which the water vapor is sprayed, in which the lactic acid aqueous solution and water vapor are mixed and sprayed at the same time.

On the other hand, the present specification, according to any one of claims 1 to 7, the method comprising the steps of vaporizing lactic acid to obtain a molecule of lactic acid;

producing acrylic acid by dehydrating the lactic acid molecules; and

Comprising the step of obtaining the acrylic acid,

A method for preparing acrylic acid is provided.

In the present invention, terms such as first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

In addition, the terminology used herein is used only to describe exemplary embodiments, and is not intended to limit the present invention.

The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present specification, terms such as “comprise”, “comprising” or “have” are used to describe an embodied feature, number, step, component, or combination thereof, and include one or more other features, number, or step. , components, combinations or additions thereof are not excluded.

Also in this specification, when it is said that each layer or element is formed "on" or "over" each layer or element, it means that each layer or element is formed directly on each layer or element, or other It means that a layer or element may additionally be formed between each layer, on the object, on the substrate.

Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

As used herein, lactic acid is a compound represented by the following formula, and unless otherwise specified in the present specification, is used as a concept encompassing all of lactic acid isomers, naturally occurring lactic acid dimers, and lactic acid oligomers.

Hereinafter, the present invention will be described in detail.

According to one aspect of the present invention, mixing spraying of a first stream of a liquid phase containing an aqueous lactic acid solution and a second stream of a gas phase containing water vapor;

vaporizing the aqueous lactic acid solution through heat exchange between the first stream and the second stream; and

obtaining a third stream of gaseous phase comprising short molecules of lactic acid;

A method for vaporizing lactic acid is provided.

The inventors of the present invention have discovered that, when a highly concentrated aqueous lactic acid solution is mixed and sprayed with water vapor and vaporized through direct heat exchange, the oligomer concentration of lactic acid can be effectively lowered in a very short time, and the present invention was completed.

Lactic acid is widely used in the production of acrylic acid. When acrylic acid is produced by dehydrating lactic acid, since it proceeds by a gas phase reaction, it is necessary to vaporize lactic acid into lactic acid molecules.

However, as described above, lactic acid is usually stored at a high concentration during storage or distribution after production. dimer) structure, or water molecules are removed to form an oligomer in the form of dehydration condensation.

Such lactic acid oligomer molecules may be carbonized in the vaporization step or reaction step to form coking, thereby reducing the active area of the reaction catalyst, and may be included as a by-product in the final product. Since the content of lactic acid in the form of single molecules that can participate is greatly reduced, it is necessary to convert the lactic acid oligomer into a single molecule in the concentrated lactic acid aqueous solution to lower the content of the oligomer and increase the content of the single molecule lactate.

However, when the concentration is diluted by simply adding water to the concentrated aqueous solution of lactic acid containing a high content of lactic acid oligomers, the equilibrium movement speed is very slow, so it takes a very long time to lower the content of the lactic acid oligomers.

In general, in order to shorten this time, a high concentration of lactic acid aqueous solution of about 80 wt% or more is heated and vaporized. Since the vaporization efficiency of lactic acid is lower than that of water, water is vaporized first, and the ratio of lactic acid in the gas phase It is less than about 20 wt%. In this case, as the water is vaporized first, the concentration of the remaining aqueous lactic acid solution is further increased. Accordingly, the concentration of the oligomer in the remaining aqueous lactic acid solution is also increased, so there is a problem that an additional treatment process is required for this.

Accordingly, in the method for vaporizing lactic acid according to an aspect of the present invention, mixing and spraying a first stream of a liquid phase containing an aqueous lactic acid solution and a second stream of a gas phase containing water vapor; vaporizing the aqueous lactic acid solution through heat exchange between the first stream and the second stream; and obtaining a third stream of gaseous phase comprising short molecules of lactic acid.

That is, according to one embodiment of the present invention, rather than directly heating and vaporizing a high-concentration aqueous lactic acid solution, a high-concentration aqueous lactic acid solution is sprayed in the form of an aerosol, but mixed and sprayed with high-temperature water vapor here, the concentration of lactic acid At the same time, it is possible to obtain vaporized lactic acid single molecules by vaporizing lactic acid through rapid heat exchange between water vapor and high concentration of lactic acid sprayed in an aerosol form.

And the concentration of lactic acid in the third stream may be about 30 wt% or less, or about 25 wt% or less, or about 20 wt% or less, and the lower limit thereof may not have much meaning depending on process conditions, but about 0.1 wt% % or more, or about 5 wt% or more.

wherein the third stream comprising single molecules of lactic acid more specifically comprises, for example, less than about 1 wt%, preferably less than about 0.5 wt%, or less than about 0.1 wt%, of the lactic acid oligomers described above. and, more preferably, substantially free of lactic acid oligomers.

Substantially free of lactic acid oligomer means that the content of lactic acid oligomer is 0 wt% within a detectable limit in the process.

According to one embodiment of the invention, the lactic acid aqueous solution included in the first stream has a lactic acid concentration of about 40 to about 99 wt%, about 45 wt% or more, or about 50 wt% or more, or about 60 wt% or more, or about 70 wt% or more, or about 75 wt% or more, and about 99 wt% or less, about 95 wt% or less, or about 90 wt% or less, or about 85 wt% or less, and may be highly concentrated. .

And, the concentration of the multimer in the aqueous lactic acid solution included in the first stream, that is, the concentration of the lactic acid dimer or trimer or more of the lactic acid oligomer is about 2 to about 55 wt%, or about 2 wt% or more, or about 5 % or more, or about 7 wt% or more, or about 8 wt% or more, about 55 wt% or less, or about 40 wt% or less, or about 20 wt% or less, the content of the multimer may be relatively high .

Here, the first stream, that is, the aqueous lactic acid solution contained in the lactic acid feed in the process is in a state in which lactic acid is dissolved in water, and as described above, naturally, depending on temperature and concentration conditions, lactic acid single molecule, lactic acid dimer, and lactic acid oligomer , and the lactic acid concentration described herein also refers to the concentration of a lactic acid-based compound including not only a single lactate molecule, but also a single lactate molecule, a lactic acid dimer, and a lactic acid oligomer.

More specifically, for example, when calculated by computer modeling based on the known oligomerization equilibrium constant value of lactic acid, the oligomer content for each concentration of the total lactic acid-based compound is shown in Table 1 below.

However, some calculation errors may appear depending on the actual calculation model, and the actual measured values may also have some measurement errors depending on the measurement conditions or measurement method (titration method or HPLC).

Concentration of total lactic acid compounds
(wt%) monomolecular concentration
(wt%) dimer concentration
(wt%) Trimer or higher concentration
(wt%) 5 5.0 0.019 0.001 10 9.9 0.079 0.011 15 14.8 0.187 0.013 20 19.6 0.35 0.05 25 24.3 0.575 0.125 30 29.0 0.874 0.126 35 33.6 1.26 0.14 40 38.0 1.75 0.25 45 42.3 2.35 0.35 50 46.3 3.11 0.59 55 50.2 4.03 0.77 60 53.8 5.18 1.02 65 56.9 6.58 1.52 70 59.6 8.31 2.09 75 61.5 10.4 3.1 80 62.5 13.0 4.5 85 62.2 16.2 6.6 90 60.1 19.8 10.1 95 55.4 23.6 16 100 47.6 26.6 25.8

And, the lactic acid aqueous solution supplied from the feed may be subjected to a heating process.

According to another embodiment of the invention, the temperature of the first stream may be about 10 to about 300 °C, preferably about 10 °C or more, or about 15 °C or more, or about 50 °C or more, and about 300 °C or less, or about 250° C. or less, or about 200° C. or less.

If the first stream is too low outside the temperature range, there may be a problem that the lactic acid is not sufficiently vaporized due to the low temperature of the mixture, and when the temperature is too high, the pressure is excessively high to maintain the temperature. can occur

The aqueous lactic acid solution supplied from the feed is heated and then sprayed in the form of droplets into the vaporization reactor through a transfer line and a nozzle. The temperature of the lactic acid aqueous solution is maintained high, so that the higher the pressure, the more advantageous it is to obtain small-sized droplets.

At this time, separately from the first stream, a second stream including water vapor is also mixed and sprayed with the first stream in the form of droplets in the vaporization reactor through a transfer line and a nozzle.

In the case of mixed spraying, after the transfer lines of the first stream and the second stream are first combined before spraying, mixed spraying may be performed through the same nozzle, but rather, the first stream and the second stream are each through separate nozzles It is more preferable to mix and spray into the gasification reactor.

The second stream temporarily lowers the concentration of lactic acid in the first stream comprising highly concentrated lactic acid while simultaneously transferring thermal energy to the first stream to promote vaporization of lactic acid molecules, thereby lowering the proportion of oligomers. can

In this respect, the temperature of the second stream may be from about 200 to about 600 °C, preferably from about 250 °C or more, or about 300 °C or more, or about 350 °C or more, or about 400 °C or more, and about 600 °C or less, or about 550° C. or less, or about 530° C. or less.

At this time, the temperature difference between the second stream and the first stream may be about 200 °C or more, or about 250 °C or more, and it may be preferably about 500 °C or less, or about 450 °C or less.

If the temperature of the second stream is too low out of the above range, the temperature of the mixture is low and lactic acid is not sufficiently vaporized. This excessively high problem may occur.

According to another embodiment of the invention, the first stream may be sprayed at a flow rate of 0.05 g/min to 1.5 g/min, and the lower limit thereof is about 0.05 g/min or more, or about 0.1 g/min or more. , or about 0.15 g/min or more, or about 0.18 g/min or more, and the upper limit thereof is preferably about 1.5 g/min or less, or about 1.0 g/min or less, or about 0.8 g/min or less. can do.

If the spraying amount and spraying rate of the first stream are too low outside the above range, the flow rate of the supplied lactic acid is too low, and there may be a problem that an overreaction proceeds in the dehydration reaction proceeding to the next step. The more heat required, the more incomplete vaporization can occur.

And, the second stream may be sprayed at a flow rate of 0.1 g/min to 4.0 g/min, and the lower limit thereof is about 0.1 g/min or more, or about 0.2 g/min or more, or about 0.3 g/min. It may be preferable to be greater than or equal to about 4.0 g/min or less, or about 3.0 g/min or less, or preferably about 2.0 g/min or less.

If the atomization amount and atomization rate of the second stream are too low outside the above range, incomplete vaporization may occur due to less heat supplied to vaporization. can occur

In this case, in the mixing spraying step, the first stream flow rate: the second stream flow rate may be preferably about 1: 1.5 to about 1: 5.

If the flow rate ratio of the first stream is too small out of the above range, the efficiency is lowered due to a small flow rate of lactic acid supplied, and problems may occur in which the load increases in the product separation process, and when the flow rate ratio of the second stream is too small , less heat is supplied to vaporization, which may lead to incomplete vaporization.

According to another embodiment of the invention, before the first stream and the second stream are mixed and sprayed in the form of droplets in the vaporization reactor through a transfer line and a nozzle, respectively, the interior of the vaporization reactor is saturated with water vapor in advance. it may be desirable

Through this method, when the first stream is sprayed into the reactor at a high temperature condition, it is possible to prevent the lactic acid from being concentrated by evaporation of water in the droplets of the first stream instantaneously sprayed under the high temperature condition.

And at this time, it may be preferable to proceed with the reaction in a state in which the vaporization reactor maintains a temperature condition of about 150 to about 250 °C.

On the other hand, the present specification, a feed supply for supplying a first stream containing an aqueous lactic acid solution; a water vapor supply unit for supplying a second stream comprising water vapor; a spray unit in which the lactic acid aqueous solution transferred from the feed supply unit and the water vapor transferred from the water vapor supply unit are mixed and sprayed; After the mixed spray, the lactic acid aqueous solution is vaporized, the vaporization reaction unit; and an harvesting unit for obtaining a third stream comprising vaporized lactic acid molecules.

In this case, the spray unit may include a lactic acid nozzle to which the aqueous lactic acid solution is sprayed and a steam nozzle to which the water vapor is sprayed, and the lactic acid aqueous solution and water vapor may be mixed and sprayed at the same time.

On the other hand, the present specification, according to any one of claims 1 to 7, the method comprising the steps of vaporizing lactic acid to obtain a molecule of lactic acid; producing acrylic acid by dehydrating the lactic acid molecules; And it provides a method for producing acrylic acid, comprising the step of obtaining the acrylic acid.

The reaction to produce acrylic acid by intramolecular dehydration of lactic acid can be represented by the following chemical formula, and is known to proceed in one step in the presence of a catalyst.

However, in the case of the method for producing acrylic acid according to one aspect of the present invention, with respect to the method for producing acrylic acid from vaporized lactic acid, except for the contents related to vaporization of lactic acid, it is generally known in the technical field to which the present invention belongs. A catalyst, a reactor, or reaction conditions may be borrowed.

For example, the catalyst used for the lactic acid dehydration reaction is CaSO ₄ / Na ₂ SO ₄ ; Na ₄ P ₂ O ₇ /CaSO ₄ ; Na ₄ P ₂ O ₇ /Ca ₃ (PO ₄ ) ₂ ; NaH ₂ PO ₄ -NaHCO ₃ /SiO ₂ ; AlPO ₄ -NH ₃ ; Ca ₃ (PO ₄ ) ₂ /CaSO ₄ and the like.

The dehydration reaction using a solid catalyst may proceed as a continuous reaction using a fixed reactor, a batch reaction, or the like. In the case of using a stationary reactor, a product can be continuously produced by charging a solid catalyst in the reactor and continuously supplying reactants to the reactor to react.

The temperature of the dehydration reaction may be from about 300 to about 500 °C, or from about 300 to about 400 °C. The reaction pressure may be from about 1 atmosphere to about 5 atmospheres, or from about 1 atmosphere to about 2 atmospheres.

The feed rate of the reactant may vary depending on the type or type of the reactor, other reaction conditions, etc., but specifically, for example, the lactic acid feed rate in the gas phase (Weight Hourly Space Velocity, WHSV) is about 0.05 to about 1.0/hr, or about 0.10 to about 0.50/hr.

When the above conditions are exceeded, a decomposition reaction by oligomerization or hydrogenation proceeds, which may cause problems in that the reaction efficiency is lowered or the conversion rate is lowered.

According to the lactic acid vaporization method and apparatus according to an aspect of the present invention, it is possible to reduce the content of lactic acid oligomers and increase the content of single lactic acid molecules in a short time in a concentrated aqueous lactic acid solution.

Hereinafter, through specific examples of the invention, the operation and effect of the invention will be described in more detail. However, these embodiments are merely presented as an example of the invention, and the scope of the invention is not defined thereby.

<Example>

An aqueous lactic acid solution having the concentration as summarized in Table 2 was prepared.

Concentration of lactic acid aqueous solution
(wt%) Initial oligomer ratio temperature
(℃) enter
(ATM) Example 1 80 0.24 25 One Example 2 80 0.23 80 One Example 3 80 0.24 80 One Example 4 70 0.15 80 One Example 5 60 0.1 80 One Example 6 80 0.23 180 10 Example 7 80 0.24 180 10

The lactic acid aqueous solution, that is, lactic acid, lactic acid dimer, and the lactic acid aqueous solution concentration of the feed containing all of lactic acid oligomer was determined by taking each sample, measuring the carbon content through elemental analysis, and dividing this by the carbon content ratio in lactic acid .

The ratio of lactic acid oligomers (including dimers) in the aqueous lactic acid solution is determined by taking each sample and analyzing the content of single lactate molecules through HPLC. It was calculated by dividing by the amount of lactic acid-based compound.

And, a feed supply unit for supplying a first stream containing the lactic acid aqueous solution; a water vapor supply unit for supplying a second stream comprising water vapor; A spray unit in which the lactic acid aqueous solution transferred from the feed supply unit and the water vapor transferred from the water vapor supply unit are mixed and sprayed through each nozzle; After the mixed spray, the lactic acid aqueous solution is vaporized, the vaporization reaction unit; and a lactic acid vaporizing device in the form of a harvesting unit for obtaining a third stream containing vaporized lactic acid molecules.

The feed supply unit and the water vapor supply unit are equipped with a thermometer and a temperature control device, so that the temperature of the feed (first stream) and water vapor (second stream) can be adjusted, and the temperature of the third stream can be measured in the obtaining unit A thermometer was provided.

First, water vapor was introduced into the vaporization reactor so that the interior of the vaporization reactor was saturated with water vapor.

After that, the lactic acid aqueous solution according to Examples 1 to 7 is supplied to the first stream through the feed supply unit, and water vapor is supplied through the water vapor supply unit, so that it is continuously mixed and sprayed into the vaporization reaction unit through each nozzle, A third stream comprising vaporized lactic acid molecules was obtained through the harvesting section.

The spray conditions are as summarized in Table 3 below.

lactic acid aqueous solution
temperature
(℃) lactic acid aqueous solution
enter
(ATM) lactic acid aqueous solution
spray amount
(g/min) water vapor temperature
(℃) water vapor atomization
(g/min) Example 1 25 One 0.6 450 1.8 Example 2 80 One 0.6 450 1.8 Example 3 80 One 0.4 500 1.2 Example 4 80 One 0.4 500 1.0 Example 5 80 One 0.2 500 0.40 Example 6 180 10 0.2 450 0.60 Example 7 180 10 0.2 500 0.35

By analyzing the obtained third stream, the concentration of total lactic acid-based compounds in the third stream and the ratio of oligomers among them were measured and calculated, and summarized in Table 4 below.

third stream
temperature
(℃) lactic acid concentration
(wt%) oligomer ratio Example 1 25 14 0.08 Example 2 80 16 0.10 Example 3 80 17 0.12 Example 4 80 15 0.06 Example 5 80 <1 0 Example 6 180 19 0.04 Example 7 180 9 0.03

Referring to Table 4, it can be clearly seen that, according to the embodiment of the present invention, the content of lactic acid oligomer can be reduced in a very short time by continuously vaporizing lactic acid.

Claims (10)

mixing and spraying a first stream of a liquid phase containing an aqueous lactic acid solution and a second stream of a gas phase containing water vapor;
vaporizing the aqueous lactic acid solution through heat exchange between the first stream and the second stream; and
obtaining a third stream of gaseous phase comprising short molecules of lactic acid;
Lactic acid vaporization method.
The method of claim 1,
The lactic acid aqueous solution contained in the first stream has a lactic acid concentration of 40 to 99 wt%, lactic acid vaporization method.
According to claim 1,
The lactic acid vaporization method, wherein the concentration of the multimer in the aqueous lactic acid solution included in the first stream is 2 to 55 wt%.
The method of claim 1,
The temperature of the first stream is 10 to 300 ℃, lactic acid vaporization method.
According to claim 1,
The temperature of the second stream is 200 to 600 ℃, lactic acid vaporization method.
According to claim 1,
The temperature difference between the second stream and the first stream is 200 to 500 °C, lactic acid vaporization method.
According to claim 1,
wherein the first stream is sprayed at a flow rate of 0.05 g/min to 1.5 g/min.
According to claim 1,
wherein the second stream is sprayed at a flow rate of 0.1 g/min to 4.0 g/min.
The method of claim 1,
In the mixing spraying step, the flow rate of the first stream: the flow rate of the second stream = 1: 1.5 to 1: 5, the lactic acid vaporization method.
10. A method comprising: vaporizing lactic acid according to the method of any one of claims 1 to 9 to obtain lactic acid molecules;
producing acrylic acid by dehydrating the lactic acid molecules; and
Comprising the step of obtaining the acrylic acid,
A method for preparing acrylic acid.