JP5785910B2 - Method for producing (meth) acrylic acid or ester thereof - Google Patents

Description

The present invention relates to a method for producing (meth) acrylic acid or an ester thereof from 3-hydroxycarboxylic acid or an ester thereof.

(Meth) acrylic acid is widely used industrially as a raw material for water-absorbing resins, etc., and usually (meth) acrylic acid is produced in the presence of an oxide catalyst using a fixed-bed multitubular continuous reactor. A two-stage oxidation method is generally used in which propylene or isobutylene is converted to acrolein or methacrolein by catalytic gas phase oxidation, and (meth) acrylic acid is produced by catalytic gas phase oxidation of the obtained acrolein or methacrolein. Since propylene and isobutylene are raw materials derived from fossil resources, it is desired to produce them from renewable resources.
Further, (meth) acrylic acid esters are produced by esterification of (meth) acrylic acid and are widely used as raw materials for various resins such as pressure-sensitive adhesives and paints.

Attempts have been made to economically produce (meth) acrylic acid on a commercial scale using biomass, which is a renewable resource. As a method for producing (meth) acrylic acid from biomass, lactic acid (2-hydroxypropionic acid, also referred to as 2HP), which is a natural product and easily available, or saccharides or cellulose obtained from natural products are decomposed. A method of preparing (meth) acrylic acid by dehydrating a hydroxypropionic acid (also referred to as HP) such as 3-hydroxypropionic acid (also referred to as 3HP) prepared by fermentation of the obtained saccharide is further mentioned.

Conventional methods include: (a) preparing a fermentation broth containing β-hydroxycarboxylic acid; (b) forming a solution containing the β-hydroxycarboxylic acid from the fermentation broth; (c) in the presence of a dehydration catalyst. Discloses a method for producing an α, β-unsaturated carboxylic acid, which comprises converting the β-hydroxycarboxylic acid to an α, β-unsaturated carboxylic acid by evaporating the solution. Further, as a dehydration catalyst, concentrated sulfuric acid, phosphoric acid, Cu—Ba—CrO catalyst, a catalyst in which phosphoric acid, phosphate, sulfate, carbonate or the like is supported on silica gel or H-β zeolite is disclosed (patent) Reference 1).
Furthermore, SiO ₂ , TiO ₂ , α-alumina, and γ-alumina are shown as catalysts when dehydrating an aqueous 3-hydroxypropionic acid solution by a gas phase reaction (see Patent Document 2).

JP-T-2005-521718 International Publication No. 2005/095320

However, it has been found that the production methods described in the above documents have the problem that the selectivity of (meth) acrylic acid is low and the problem of causing coking on the catalyst. Therefore, the present inventors have found the following various problems.
In the process for producing (meth) acrylic acid, when dehydrating 3-hydroxycarboxylic acid, it was found that side reactions such as decomposition by decarboxylation and generation of short-chain carboxylic acid occur. The selectivity of was found to be low. This is particularly noticeable when the conversion rate of 3-hydroxycarboxylic acid is high.
In addition, (meth) acrylic acid, which is a product in the production process of (meth) acrylic acid, is easily adsorbed on the dehydration catalyst disclosed in the above-mentioned document and easily causes coking, so that the activity of the catalyst is greatly reduced. I found out. Furthermore, in the raw material 3-hydroxycarboxylic acid used in the production method of (meth) acrylic acid, oligomers and N-containing compounds may be mixed in the raw material. When a general dehydration catalyst is used, oligomers and N It has been found that the contained compound adheres firmly to the dehydration catalyst and coking easily occurs. When there is a large amount of coking, the catalyst's activity decreases quickly, requiring frequent catalyst regeneration and catalyst replacement, resulting in a decrease in productivity and coke generated inside the catalyst. It has also been found that there are harmful effects such as clogging of the vessel and shortened catalyst life.

Therefore, there is room for improvement in improving the conversion rate of 3-hydroxycarboxylic acid and the selectivity of (meth) acrylic acid, reducing coking on the catalyst, and efficiently producing (meth) acrylic acid. It was.

Therefore, the object of the present invention is to suppress the side reaction when producing (meth) acrylic acid or its ester using 3-hydroxycarboxylic acid or its ester as a raw material, and the conversion rate of 3-hydroxycarboxylic acid or its ester. And (meth) acrylic acid or its ester selectivity is improved, and coking on the catalyst is reduced to suppress a decrease in catalyst activity, a reactor blockage, etc., and a high purity (meth) acrylic acid Another object of the present invention is to provide a method for producing (meth) acrylic acid or an ester thereof, which can efficiently produce the ester.

As a result of various studies to solve the above-mentioned problems, the present inventors have produced 3-hydroxycarboxylic acid or its ester in producing (meth) acrylic acid or its ester from a raw material composition containing 3-hydroxycarboxylic acid or its ester. By using a specific oxide containing an alkali metal element and / or an alkaline earth metal element as a dehydration catalyst used in a dehydration step of dehydrating the ester to produce (meth) acrylic acid or an ester thereof , Suppressing side reactions, improving the conversion rate of 3-hydroxycarboxylic acid or its ester and the selectivity of (meth) acrylic acid or its ester, and reducing coking on the catalyst, It is possible to efficiently produce high-purity (meth) acrylic acid or its ester by suppressing reduction and reactor blockage. And they found that, the present invention has been completed.

That is, the present invention is a method for producing (meth) acrylic acid or an ester thereof from a raw material composition containing 3-hydroxycarboxylic acid or an ester thereof, and the production method comprises the 3-hydroxycarboxylic acid or an ester thereof. A dehydration step of generating (meth) acrylic acid or an ester thereof by dehydrating an ester, the dehydration step is performed using a dehydration catalyst, and the dehydration catalyst is represented by the following general formula (1):
M _a X _b Y _c O _d (1)
Wherein M is at least one element selected from the group consisting of alkali metals and alkaline earth metals; X is at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium; Y is boron and phosphorus At least one element selected from the group consisting of: O represents oxygen, a is 1, b is a number from 1 to 300, c is a number from 0 to 0.8, d is a value of a, b, c and various configurations. (The value is determined by the bonding state of the element.)
(Meth) acrylic acid or its ester manufacturing method characterized by being an oxide represented by these.
Moreover, this invention is the said manufacturing method characterized by the said 3-hydroxycarboxylic acid being 3-hydroxypropionic acid.

According to the method for producing (meth) acrylic acid or ester thereof of the present invention, side reaction is suppressed, and the conversion rate of 3-hydroxycarboxylic acid or ester thereof and the selectivity of (meth) acrylic acid or ester thereof are improved. In addition, coking on the catalyst can be reduced to suppress a decrease in catalyst activity, a clogging of the reactor, and the like, and high-purity (meth) acrylic acid or an ester thereof can be efficiently produced.

Hereinafter, the present invention will be described in detail.
A combination of two or more preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

The method for producing (meth) acrylic acid or an ester thereof according to the present invention is a method for producing (meth) acrylic acid or an ester thereof from a raw material composition containing 3-hydroxycarboxylic acid or an ester thereof. It includes a dehydration step of producing a (meth) acrylic acid or an ester thereof by dehydrating a carboxylic acid or an ester thereof, and the dehydration step is performed using a specific dehydration catalyst.

The dehydration catalyst used in the present invention (hereinafter also simply referred to as “catalyst”) is represented by the general formula (1):
M _a X _b Y _c O _d (1)
Wherein M is at least one element selected from the group consisting of alkali metals and alkaline earth metals; X is at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium; Y is boron and phosphorus At least one element selected from the group consisting of: O represents oxygen, a is 1, b is a number from 1 to 300, c is a number from 0 to 0.8, d is a value of a, b, c and various configurations. (The value is determined by the bonding state of the element.)
It is an oxide represented by.

In the following description, at least one element selected from the group consisting of alkali metals and alkaline earth metals represented by M in the above general formula (1) is M element; silicon, aluminum represented by X At least one element selected from the group consisting of titanium and zirconium is also referred to as X element; at least one element selected from the group consisting of boron and phosphorus represented by Y is also referred to as Y element.

In General formula (1), the ratio of M element and X element is 1: 1-300. That is, b is 1 to 300. From the viewpoint of catalytic activity, b is preferably 1.5 to 250, more preferably 2 to 200, and still more preferably 2.5 to 150.
Moreover, the ratio of the M element and the Y element added as necessary is 1: 0 to 0.8. That is, c is 0 to 0.8. From the viewpoint of catalytic activity and maintenance of activity, c is preferably 0.01 to 0.8, more preferably 0.03 to 0.8, and still more preferably 0.05 to 0.8.
d is a numerical value determined by the values of a, b and c and the bonding state of various constituent elements, and is preferably 2 to 600, more preferably 3 to 400, and still more preferably 5 to 5 from the viewpoint of catalyst stability. 300.

In general formula (1), M, X, and Y may each include a plurality of elements. M may contain two or more elements selected from the group consisting of alkali metals and alkaline earth metals. X may contain two or more elements selected from the group consisting of silicon, aluminum, titanium and zirconium. Y may contain both boron and phosphorus. Moreover, it is preferable that M, X, and Y each contain one or two elements.
When M, X, and Y are each composed of a plurality of elements, the subscript a represents the total number of atoms of the plurality of elements selected from the group consisting of alkali metals and alkaline earth metals, and b represents silicon, aluminum, and titanium. And the total number of atoms of a plurality of elements selected from the group consisting of zirconium and c represents the total number of atoms of boron and phosphorus.
In the general formula (1), the numerical values of b, c, and d when the a representing the total number of atoms of an element selected from the group consisting of alkali metals and alkaline earth metals is 1 are described. Yes.

Examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium and francium, preferably sodium, potassium and cesium.
Examples of the alkaline earth metal include beryllium, magnesium, calcium, strontium, barium and radium, preferably magnesium, calcium and barium.
M is preferably sodium, potassium, cesium or barium, more preferably sodium, potassium or cesium.
X is preferably silicon or aluminum, and more preferably silicon.
Y is preferably phosphorus.

By the way, as described above, during the dehydration reaction of 3-hydroxycarboxylic acid or ester thereof, side reactions such as decomposition by decarboxylation and generation of short-chain carboxylic acid are likely to occur, so (meth) acrylic acid or ester thereof This is particularly noticeable when the conversion of 3-hydroxycarboxylic acid or its ester is high. Further, (meth) acrylic acid or an ester thereof, which is a product in the production method of (meth) acrylic acid or an ester thereof, is easily adsorbed on a general dehydration catalyst, and thus easily causes coking. However, the dehydration catalyst in the present invention has small side reactions and relatively low coking, and even if coking occurs, the catalyst activity is gradually reduced. This effect is considered to be due to the configuration of the catalyst in the present invention. In other words, the catalyst in the present invention can be selected by appropriately selecting the type, number, and ratio of the M element, X element and / or Y element, so that the number of acid points and base points on the catalyst, the strength, the acid point / base point. Control the distance between them, and adsorb 3-hydroxycarboxylic acid or its ester on the catalyst, desorb water molecules from the hydroxyl group as the reaction site, and desorb the (meth) acrylic acid or its ester. It is considered that the dehydration reaction proceeds moderately without any shortage, suppressing side reactions such as decomposition reactions and coking.

The method for preparing the dehydration catalyst is not particularly limited, and any conventionally known method can be applied.
The element M is used as a raw material for oxides, hydroxides, halides, salts (carbonates, nitrates, carboxylates, phosphates, sulfates, etc.) of alkali metal elements and / or alkaline earth metal elements. The metal itself is used.
Among the above X elements, silicon is used as a raw material of silicon oxide, silicic acid, silicates (alkali metal silicate, alkaline earth metal silicate, etc.), silicon-containing zeolite (aluminosilicate, silicoaluminophosphate, etc.) ), And organic silicate esters are used. Examples of zeolite include A type, X type, Y type, X type, ZSM-5 type, and β type. As the raw materials of aluminum, titanium and zirconium, respective oxides, hydroxides, halides, alkoxides and salts (carbonates, nitrates, carboxylates, phosphates, sulfates, etc.) are used.
As the raw material of the Y element added as necessary, phosphoric acid, phosphate, boric acid, borate and oxide are used.

Examples of the method for preparing the catalyst in the present invention include the following methods. (1) A method in which an M element source and an X element source are dissolved or suspended in water, heated and concentrated under stirring, molded after drying, and used as a catalyst through firing. (2) A method in which a silicon oxide molded body is immersed in an aqueous solution of an M element source, then heated to dryness, dried and fired to form a catalyst. (3) A method in which an aqueous solution of an M element source is added to and mixed with various silicates or silicon-containing oxides, followed by drying, molding, firing, and the like as a catalyst. (4) A method in which a silicon-containing zeolite is doped with an M element source by an ion exchange method, followed by drying, molding, firing, and the like to be a catalyst.
In the above (2) to (3), the case where the X element is silicon is described, but the case where the X element is aluminum, titanium, or zirconium can be obtained in the same manner as described above.
Moreover, in order to make a catalyst contain Y element, the raw material which contains Y element in M element source or X element source may be used, and the raw material of Y element may be added in the middle of catalyst preparation.

Furthermore, the catalyst can be used by being supported or mixed on a known carrier (for example, silica, alumina, silicon carbide, etc.).
The calcination temperature of the catalyst is preferably 300 to 1000 ° C, more preferably 400 to 800 ° C, although it depends on the type of catalyst raw material used.
The calcination time of the catalyst is not particularly limited, but is preferably 0.2 to 24 hours, and more preferably 0.5 to 12 hours.

Further, it is used for producing (meth) acrylic acid or an ester thereof by dehydrating 3-hydroxycarboxylic acid or an ester thereof, and the following general formula (1):
M _a X _b Y _c O _d (1)
Wherein M is at least one element selected from the group consisting of alkali metals and alkaline earth metals; X is at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium; Y is boron and phosphorus At least one element selected from the group consisting of: O represents oxygen, a is 1, b is a number from 1 to 300, c is a number from 0 to 0.8, d is a value of a, b, c and various configurations. (The value is determined by the bonding state of the element.)
A catalyst for producing (meth) acrylic acid or an ester thereof, which is an oxide represented by the formula (1), is also one aspect of the present invention.

In addition, in this specification, unless otherwise indicated, about 3-hydroxycarboxylic acid or its ester, 3-hydroxycarboxylic acid is described as these representatives, and about (meth) acrylic acid or its ester, (Meth) acrylic acid is described as a representative of these. In addition, 3-hydroxycarboxylic acid ester and (meth) acrylic acid ester can each be obtained by esterifying a corresponding acid by the method mentioned later.

Examples of the 3-hydroxycarboxylic acid in the present invention include 3-hydroxypropionic acid (hereinafter also referred to as 3HP), 3-hydroxyisobutyric acid, and the like, and preferably 3-hydroxypropionic acid. Moreover, as (meth) acrylic acid, acrylic acid and methacrylic acid are mentioned, Preferably it is acrylic acid.
The said 3-hydroxycarboxylic acid can be used by 1 type or 2 types. Moreover, (meth) acrylic acid is obtained according to the kind of 3-hydroxycarboxylic acid used.

The raw material composition containing 3-hydroxycarboxylic acid only needs to contain the 3-hydroxycarboxylic acid, and may contain an ester dimer, an ether dimer, an oligomer of trimer or higher, and the like of 3-hydroxycarboxylic acid. Moreover, the by-product etc. which are produced | generated in preparation of a solvent and 3-hydroxycarboxylic acid may be included.
The concentration of the total amount of 3-hydroxycarboxylic acid and its ester contained in the raw material composition is preferably 5 to 95% by mass, more preferably 7 to 90% by mass, and still more preferably 10 to 90% by mass.

The raw material composition containing 3-hydroxycarboxylic acid may contain a solvent. The solvent is not particularly limited as long as it can dissolve 3-hydroxycarboxylic acid, and examples thereof include water, alcohol, hydrocarbon, ether, ketone, ester, amine, and amide. These can be used alone or in combination of two or more. The boiling point of the solvent is preferably lower than 3-hydroxycarboxylic acid because vaporization is easy. Water is preferred.
In the present invention, when a solvent is contained in the raw material composition, the concentration of the solvent in 100% by mass of the raw material composition is preferably 5 to 95% by mass, more preferably 10 to 93% by mass, and still more preferably 10%. It is -90 mass%. If the concentration of the solvent is 5% by mass or more, handling of the raw material composition is facilitated due to a decrease in viscosity, and an effect of promoting the evaporation of 3-hydroxycarboxylic acid can be expected. On the other hand, by setting it as 95 mass% or less, it can suppress the calorie | heat amount concerning evaporation and can contribute to reduction of utility cost.

The raw material composition containing 3-hydroxycarboxylic acid may contain components other than 3-hydroxycarboxylic acid, for example, by-products when synthesizing 3-hydroxycarboxylic acid by fermentation or the like. Specific examples of the by-products include formic acid, acetic acid, propionic acid, butyric acid, succinic acid, fumaric acid, pyruvic acid, glycolic acid, and lactic acid, which may be by-produced together with 3-hydroxycarboxylic acid in fermentation. , Ethanol, amino acids, 1,3-propanediol, glycerin, hydroxypropionaldehyde, alanine and the like.

The 3-hydroxycarboxylic acid used in the present invention can be obtained from various sources, and from the viewpoint of global warming and environmental protection, it is preferable to use a biological resource that can be recycled as a carbon source.
As 3-hydroxycarboxylic acid, 3-hydroxypropionic acid, 3-hydroxyisobutyric acid, etc. prepared by fermentation from saccharides obtained by decomposing saccharides obtained from agricultural crops, cellulose, etc. can be used.
In this invention, it is preferable that at least one part or all of 3-hydroxycarboxylic acid contained in a raw material composition is 3-hydroxycarboxylic acid obtained by fermentation.
Moreover, it is preferable that it is biological origin resources, such as biomass, as a raw material of 3-hydroxycarboxylic acid.

3-Hydroxycarboxylic acid is available by a known method. For example, glucose is used as a carbon source using beta-alanine aminotransferase gene-transferred Escherichia coli derived from Streptomyces griseus ATCC21897 described in International Publication No. 2008/027742. Can be obtained by fermentation. It can also be obtained by fermentation using glycerin as a carbon source using Klebsiella pneumoniae-derived glycerin dehydrase and Escherichia coli-derived aldehyde oxidase-introduced Escherichia coli described in International Publication No. 2001/016346.

As the raw material composition containing 3-hydroxycarboxylic acid used in the present invention, it is preferable to use a raw material composition with fewer impurities.
As a method for obtaining a raw material composition with few impurities, a known method can be used. Specifically, the crude 3-hydroxycarboxylic acid obtained by fermentation is precipitated using a calcium salt and recovered as a calcium salt of 3-hydroxycarboxylic acid, and then reacted with an acid such as sulfuric acid to produce 3 -A method of purifying hydroxycarboxylic acid; a method of chemically converting ammonium-type 3-hydroxycarboxylic acid obtained by fermentation into 3-hydroxycarboxylic acid by electrodialysis or a cation exchange method;
In addition, an ammonium solvent-type 3-hydroxycarboxylic acid aqueous solution obtained by fermentation is heated by adding an immiscible amine solvent to water, thereby removing ammonia and obtaining an amine solution of 3-hydroxycarboxylic acid. be able to. An aqueous solution of 3-hydroxycarboxylic acid can be obtained by adding water thereto and heating.
It can also be purified by evaporation utilizing the vapor pressure of 3-hydroxycarboxylic acid. However, since the vapor pressure of 3-hydroxycarboxylic acid is small and side reactions such as oligomerization are likely to proceed by heating, an evaporation method with a small thermal history such as thin layer evaporation under reduced pressure is preferred.
Further, the 3-hydroxycarboxylic acid is esterified with an alcohol, and the obtained 3-hydroxycarboxylic acid ester is purified by distillation, and then the 3-hydroxycarboxylic acid ester is hydrolyzed to obtain a purified 3-hydroxycarboxylic acid. You can also get

In addition, the raw material composition used in the present invention may contain an inorganic compound that is a medium component used in the fermentation process. Examples of inorganic compounds include disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, iron chloride, sulfuric acid Examples include magnesium, sodium sulfate, manganese sulfate, zinc sulfate, iron sulfate, copper sulfate, and ammonium acetate.
If an inorganic compound is present in the raw material composition, in the case of a gas phase reaction, the inorganic compound may precipitate in the evaporator, resulting in clogging or a decrease in evaporation efficiency. Hydroxycarboxylic acid may be modified in the evaporator to become an oligomer or other by-product, leading to a decrease in (meth) acrylic acid yield. Moreover, when an inorganic compound adsorb | sucks to a catalyst, the fall of catalyst activity and the fall of (meth) acrylic acid selectivity may be caused.
The amount of the inorganic compound is preferably 1% by mass or less, more preferably 0.5% by mass or less, with respect to 100% by mass of the total amount of 3-hydroxycarboxylic acid and its ester in the raw material composition, A mass% or less is more preferable. If the amount of the inorganic compound is 1% by mass or less, side reactions such as blockage due to precipitation in the evaporator and oligomerization of 3-hydroxycarboxylic acid can be suppressed, and reduction in the activity of the catalyst can also be suppressed in the dehydration step. Therefore, long-term stable operation is possible.

The method for producing (meth) acrylic acid of the present invention includes a dehydration step of producing (meth) acrylic acid by dehydrating 3-hydroxycarboxylic acid using the specific dehydration catalyst. The process can be either a liquid phase reaction or a gas phase reaction. In order to increase the activity of the catalyst and increase the productivity, the gas phase reaction is preferred. The gas phase reaction can be carried out by vaporizing a raw material composition containing 3-hydroxycarboxylic acid and bringing the vaporized gas into contact with the specific dehydration catalyst to perform a dehydration reaction.

Vaporization (evaporation) of the raw material composition containing 3-hydroxycarboxylic acid can be carried out by heating the composition. The temperature in the evaporator is preferably 150 ° C to 500 ° C, more preferably 170 ° C to 480 ° C, further preferably 200 ° C to 460 ° C, particularly preferably 220 ° C to 440 ° C, and most preferably 220 ° C to 420 ° C. . If the said temperature is the range of 150 to 500 degreeC, a raw material composition will vaporize rapidly and the obstruction | occlusion of the evaporator and reactor by side reaction will not arise. Further, when the temperature is higher than 500 ° C., not only the energy required for heating becomes excessive, but the composition may cause coking, and carbonaceous deposits may adhere to the evaporator or the reactor and cause clogging. is there.

The lower the pressure in the evaporator, the easier the evaporation of the raw material composition occurs, which is advantageous. However, it is necessary to select the appropriate pressure of the subsequent reactor and the cost of equipment and the like. As a pressure in an evaporator, Preferably it is 10 kPa-1000 kPa, More preferably, it is 30 kPa-300 kPa, More preferably, it is 50 kPa-250 kPa.

The evaporator preferably has a structure for efficiently transferring heat to the raw material composition supplied as a liquid. For example, a horizontal tube type or a vertical tube type natural circulation evaporator, forced circulation evaporator and the like can be mentioned.
In addition, in the flow path of the raw material composition in the evaporator, irregular packing and rules such as Raschig rings, Berle saddles, spherical moldings, wire mesh moldings (Dixon packing, McMahon packing, etc.), Merapack (made by Sulzer Chemtech) A method of evaporating by filling a filler having a large surface area per unit filling volume, such as a filler, and supplying the raw material composition thereto to increase the surface area in contact with the raw material composition (liquid) can also be mentioned. By doing so, the supplied raw material composition comes into contact with the packing having a large surface area, the heat transfer area is increased, the heat is transferred efficiently, and the evaporation proceeds in a short time. The conversion rate of the raw material composition becomes low.
As the material for the filler, a metal material such as iron or stainless steel, an inorganic material such as silica or ceramic, or the like can be used.
Alternatively, the raw material composition may be supplied to a fluidized bed evaporator and vaporized. For example, a powdery inert solid may be fluidized with an inert gas, and the raw material composition may be supplied to a heated fluidized bed evaporator and vaporized.

A preferable form in the evaporation step is a form in which gas is evaporated while introducing gas (water, inert gas, etc.) during heating. When a gas such as water or an inert gas is introduced together with the raw material composition, evaporation of 3-hydroxycarboxylic acid is promoted and a stable reaction can be continued, which is a preferable mode.
Examples of the gas include nitrogen, helium, argon, carbon dioxide, water vapor evaporated water, and the like, and these can be used alone or in combination. Nitrogen and water vapor are preferable. The water vapor includes water vapor obtained by vaporizing water contained as a solvent in the raw material composition.
The amount of gas supplied is preferably 0.5 to 100 moles as the total amount of water and / or inert gas with respect to the total amount of 3-hydroxycarboxylic acid and its oligomer in the raw material composition, preferably 1 mole. Double to 50 mole times is more preferable.

Next, as the reactor used in the dehydration step, it is sufficient that the solid catalyst is held therein and heated, and for example, a fixed bed continuous reactor, a fluidized bed continuous reactor, etc. can be used. A vessel is preferred.
In the case of using the above fixed bed continuous reactor, the catalyst is filled in the reactor and heated, and the raw material composition vapor is supplied thereto. As the vapor of the raw material composition, any of an upward flow, a downward flow, and a horizontal flow can be suitably used. In addition, a fixed-bed multitubular continuous reactor can be suitably used because of easy heat exchange.
When the above fluidized bed continuous reactor is used, a powdered catalyst is placed in the reactor, and the reaction can be carried out while the catalyst is fluidized with the vapor of the raw material composition or an inert gas supplied separately. . Since the catalyst is flowing, clogging due to heavy components hardly occurs. It is also possible to continuously extract a part of the catalyst and continuously supply a new catalyst or a regenerated catalyst.

The dehydration step may be after the evaporation step, and another step may be provided between them. For example, the dehydration step may be performed in the reactor through a temperature adjustment step in which the vapor of the raw material composition vaporized in the evaporator is heated / cooled to a predetermined temperature.
Further, the evaporator and the reactor may be integrated. For example, a continuous operation in which a reaction tube is filled with a packing having a large surface area as an evaporation layer, and a catalyst is filled under the evaporation layer, the evaporation layer serves as an evaporation step, and the catalyst layer serves as a dehydration step. It is one of.
It is also a preferred form to operate by connecting one or a plurality of evaporation layers and a multi-tube reactor filled with a catalyst.

As the dehydration catalyst, the catalyst represented by the general formula (1) is used.
The catalyst may be a powder or a molded body. The shape of the formed body is not limited, and examples thereof include a spherical shape, a cylinder shape, a ring shape, and a honeycomb shape. The form of the catalyst can be selected according to the type of reaction used. In the case of a fixed bed reactor, a molded body is preferable in order to reduce the pressure loss, and in the case of a fluidized bed reactor, powder is more preferable for flowing the catalyst.

The feed rate of the raw material composition to the reactor is determined from the viewpoint of maintaining the conversion rate of 3-hydroxycarboxylic acid and suppressing the decrease in the activity of the catalyst. The total amount of GHSV (space velocity) of gas and the like is preferably 1 to 100,000 / hour, more preferably 2 to 50000 / hour, and still more preferably 6 to 30,000 / hour. GHSV is defined as a value obtained by dividing the gas volume flow rate (0 ° C., 101 kPa conversion) calculated from the raw material composition and the gas composition by the volume of the catalyst layer. The GHSV can be adjusted by changing the feed rate of the raw material composition or the inert gas.

The temperature of the catalyst layer is preferably maintained at 150 ° C to 500 ° C. More preferably, it is 200 to 450 degreeC, More preferably, it is 220 to 430 degreeC, Most preferably, it is 250 to 400 degreeC. Within this temperature range (150 ° C. to 500 ° C.), the reaction rate is high, side reactions are unlikely to occur, and the yield of (meth) acrylic acid increases.
The reaction pressure is not particularly limited, but can be determined in consideration of the evaporation method of the raw material composition, the productivity of the dehydration reaction, the collection efficiency after the dehydration reaction, and the like. The reaction pressure is preferably 10 kPa to 1000 kPa, more preferably 30 kPa to 300 kPa, and even more preferably 50 kPa to 250 kPa.

Although the dehydration reaction of 3-hydroxycarboxylic acid can be stably maintained by the evaporation step and the dehydration step, a carbonaceous substance (coke) may be gradually deposited on the catalyst. In that case, there is a possibility that problems such as a decrease in productivity and a decrease in selectivity due to a decrease in catalyst activity may occur. In that case, it can return to a normal state by removing the produced carbonaceous material.

In order to remove the carbonaceous material on the dehydration catalyst, the catalyst can be regenerated by bringing the dehydration catalyst into contact with an oxidizing agent to remove the carbonaceous material.
As the oxidizing agent, a liquid oxidizing agent in which hydrogen peroxide solution, organic peroxide, nitric acid, nitrous acid or the like is dissolved may be used, or a gaseous oxidizing agent may be used. A gaseous oxidant is preferred.
A gaseous oxidant is a gas molecule capable of supplying an elemental oxygen to the carbonaceous material for oxidative decomposition of the carbonaceous material, for example, oxygen (oxygen in the air also corresponds to the oxidant). , Ozone, nitric oxide, nitrogen dioxide, dinitrogen monoxide and the like. Of these oxidizers, one or more gaseous oxidizers may be included. For example, a mixed gas of air and oxygen, a mixed gas of nitrogen monoxide and oxygen, or the like may be used. A mixed gas of at least one gas arbitrarily selected from inert gases such as nitrogen, carbon dioxide, argon, helium and water vapor and an oxidizing agent may be used. A gas containing oxygen is preferable.

In the catalyst regeneration, the catalyst regeneration time can be shortened as the catalyst is heated to a higher temperature. However, if it is too high, the catalyst activity and selectivity may decrease due to a change in the structure of the catalyst. Usually, a preferable range is 300-800 degreeC, More preferably, it is 320-700 degreeC, More preferably, it is 350-600 degreeC. When the temperature exceeds 800 ° C., the catalytic structure and chemical properties of the catalyst change, such as a decrease in the catalyst surface area due to sintering and a change in the crystal structure of the catalyst due to phase transition. There is a fear. The upper limit of the temperature varies depending on the catalyst type, but when the catalyst is calcined during catalyst preparation, it is preferable to heat at a temperature not exceeding the calcining temperature.

In order to control the heating temperature, it is preferable to adjust the set temperature of the heater for heating the catalyst, the oxidant concentration, the gas flow rate, and the like. In this case, the higher the set temperature of the heater and / or the oxidant concentration, the higher the temperature at which the catalyst is heated. It is also possible to control the catalyst heating temperature by adjusting the set temperature of the heater and / or the concentration of the oxidizing agent while continuously measuring the catalyst heating temperature. Moreover, the control method of the catalyst heating temperature currently disclosed by Unexamined-Japanese-Patent No. 5-192590 is also mentioned.
The oxidant concentration is preferably 1 to 21% by volume from the viewpoint of temperature control, production cost, and the like.
The treatment time is preferably 1 to 100 hours, more preferably 2 to 50 hours, from the viewpoint of productivity of (meth) acrylic acid.

In the method according to the present embodiment for removing the carbonaceous material by oxidative decomposition, depending on the type of the catalyst, the catalytically active component may be scattered during the dehydration reaction process or the oxidative decomposition process of the carbonaceous material. In such a case, replenishment processing of the catalytically active component is performed according to the required catalytic activity. As a catalyst that is preferably subjected to the replenishment treatment, a catalyst in which the Y element is phosphorus is exemplified. When phosphorus scattered in the process of dehydration of 3-hydroxycarboxylic acid or the process of oxidative decomposition and removal of carbonaceous substances is supplemented, the activity is restored.

In order to perform the replenishment process of the catalyst active component, it is preferable to re-execute the method of supporting the active component in the catalyst preparation. As this method, for example, (1) a method of replenishing a catalyst extracted from a reaction tube by a method such as impregnation with a predetermined amount of a catalytically active component, (2) disclosed in JP-A-2-290255. The method of replenishing a catalyst active component by the process which makes a volatile compound (compound containing phosphorus element, such as phosphate ester) contact the catalyst of the state with which the reaction tube was filled by the method etc. is mentioned.

In the present invention, the method of cooling the reaction product obtained from the reactor outlet to obtain the composition containing (meth) acrylic acid is not particularly limited. For example, the reaction product gas is converted into a heat exchanger. And (meth) acrylic acid is cooled by a method obtained by condensing at a temperature below the dew point of the reaction product gas or a method of absorbing the reaction product gas by contacting with a collection agent such as a solvent. A composition can be obtained.
The (meth) acrylic acid concentration in the composition is preferably 5 to 95% by mass, more preferably 10 to 95% by mass, and still more preferably 20 to 95% by mass.

The reaction product composition thus obtained contains water and (meth) acrylic acid, which are the main reaction products, and other by-products and solvents and impurities in the raw material composition. May be included. When the solvent is water, it can be used as a raw material for polymer production in the form of an aqueous solution of (meth) acrylic acid. Moreover, high purity (meth) acrylic acid can be obtained by adding a purification step.
A refinement | purification process can be implemented by well-known techniques, such as distillation, extraction, membrane separation, and crystallization, and may implement it combining them.
The reaction product containing (meth) acrylic acid obtained as described above is preferably subjected to collection and purification processes in the presence of a polymerization inhibitor. Examples of the polymerization inhibitor include methoquinone, manganese acetate, nitrosophenol, cuperone, N-oxyl compound, copper dibutylthiocarbamate, phenothiazine, hydroquinone and the like. Moreover, you may supply oxygen-containing gas as needed.

Thus, highly purified (meth) acrylic acid can be obtained by refine | purifying the composition of (meth) acrylic acid obtained by this invention. Therefore, the method of the present invention also provides a method for producing high-purity (meth) acrylic acid.
Specifically, the method includes a step of purifying (meth) acrylic acid or an ester thereof by crystallization.

The gaseous reaction product is liquefied by cooling condensation, solvent collection, or the like, and water or collection solvent contained in the liquefied product is removed by a conventionally known method (for example, distillation) as necessary. A method for obtaining high-purity (meth) acrylic acid by a crystallization method will be described below.
Here, crude (meth) acrylic acid refers to a composition containing (meth) acrylic acid obtained in the cooling step, and an aqueous solution of (meth) acrylic acid is particularly preferably used.
In the crystallization step, a conventionally known method capable of separating propionic acid from crude (meth) acrylic acid, for example, a method described in JP-A-9-227445 or JP-A-2002-519402 is used. Can be done.

(Meth) acrylic acid can be produced by the above method. The (meth) acrylic acid thus produced is, as already known, (meth) acrylic acid derivatives such as (meth) acrylic acid esters; poly (meth) acrylic acid, poly (meth) acrylic acid sodium, etc. It is useful as a raw material for the synthesis of such hydrophilic resins. Therefore, the method for producing (meth) acrylic acid according to the present invention can naturally be incorporated into a method for producing a (meth) acrylic acid derivative or a hydrophilic resin.

In the method of the present invention, as in the production of (meth) acrylic acid by the dehydration reaction of 3-hydroxycarboxylic acid, the production of (meth) acrylic acid ester by the dehydration reaction of 3-hydroxycarboxylic acid ester is also efficiently carried out. be able to.

The 3-hydroxycarboxylic acid ester can be synthesized by esterifying 3-hydroxycarboxylic acid with an alcohol.
It does not specifically limit as alcohol to be used, What is necessary is just to select according to a use, However, C1-C20 alcohol is preferable, C1-C10 alcohol is more preferable, C1-C5 More preferred is alcohol.

The esterification reaction can be achieved by heating the 3-hydroxycarboxylic acid and alcohol in the presence or absence of an esterification catalyst. Since 3-hydroxycarboxylic acid is a carboxylic acid, the esterification reaction proceeds even in the absence of a catalyst. However, it is preferable to use an esterification catalyst from the viewpoint of production efficiency.
As the esterification catalyst, known catalysts can be used, but mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; solid acids such as zeolite and ion exchange resin; inorganic acids such as heteropolyacid; p-toluenesulfonic acid and the like Sulphonic acids of the above; metal compounds such as dibutyltin dilaurate, tin oxide, dibutyltin oxide, zinc acetate, tetraalkoxytitanium;
The reaction temperature is preferably 50 ° C to 300 ° C, more preferably 80 ° C to 250 ° C.
Since the esterification reaction is an equilibrium reaction, reactive distillation and reaction while extracting the product are also effective for improving the yield.
Moreover, 3-hydroxycarboxylic acid ester can also be synthesize | combined from 3-hydroxycarboxylic acid and alcohol using microorganisms.

From the 3-hydroxycarboxylic acid ester, a (meth) acrylic acid ester can be obtained through the above-described steps.
The reaction product thus obtained contains (meth) acrylic acid ester and water, which are the main reaction products, and other (meth) acrylic acid, by-products and raw material compositions. May contain solvents and impurities. In that case, a highly purified (meth) acrylic acid ester can be obtained by adding a purification step. A refinement | purification process can be implemented by well-known techniques, such as distillation, extraction, membrane separation, and crystallization, and may implement it combining them.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and appropriate modifications are made within a range that can meet the purpose described above and below. Any of these can be carried out and are included in the technical scope of the present invention.
Unless otherwise specified, “%” indicates “mass%” and “part” indicates “mass part”.

(Preparation Example 1) Method for Obtaining Composition Containing 3-Hydroxypropionic Acid (3HP) Production of 3HP by fermentation was performed according to the method of Example 1 of JP2012-085635A. Bacterial cells were separated from the obtained fermentation broth by filtration, 100 g of n-dodecanol was added to 700 g of the obtained filtrate, and water was distilled off by an evaporator. Finally, it was performed at 50 ° C. and 2.7 kPa until no distillation occurred.
The obtained residual liquid was applied to a thin film evaporator at 80 ° C. and 10 Pa to obtain a mixture of 3HP and n-dodecanol as a fraction. An equal amount of water was added to the obtained fraction and mixed to extract 3HP in the aqueous phase. An equal amount of water was again added to the oily phase separated from oil and water, and 3HP was extracted. The aqueous phases separated into oil and water were combined and filtered to obtain a 3HP aqueous solution. The concentration of 3HP was 16% by mass. Water was added to the obtained 3HP aqueous solution to adjust to 12% by mass, and this aqueous solution was used as a raw material composition for dehydration reaction.

Example 1
(Preparation of catalyst)
2.1 g of lithium sulfate monohydrate was dissolved in 100 g of water, 20 g of silicon oxide was added with heating and stirring at 90 ° C., concentrated and dried, and then dried at 120 ° C. in an air atmosphere for 20 hours. The obtained solid was coarsely pulverized and further calcined in air at 500 ° C. for 2 hours to obtain a catalyst whose composition excluding oxygen was Li ₁ Si ₁₀ . The obtained catalyst was crushed to 10 to 24 mesh and used for dehydration reaction.
(Dehydration reaction)
A stainless steel tube having an inner diameter of 10 mm was filled with 1.5 mm Dixon packing made of stainless steel as an evaporation layer, and the evaporator was installed in an electric furnace. Further, a stainless steel tube having an inner diameter of 10 mm was filled with 2.2 ml of the above catalyst, and installed in an electric furnace to prepare a reactor. The outlet of the evaporator and the inlet of the reactor were connected with a stainless steel tube so that the surroundings could be heated with an electric heater.
Further, the temperature in the evaporator was 275 ° C., the temperature in the reactor was 300 ° C., and the 12% by mass aqueous solution of 3-hydroxypropionic acid obtained in Preparation Example 1 was evaporated at a rate of 16.7 g per hour. Supplied to the top of the vessel. At the same time, nitrogen gas was allowed to flow at a rate of 3 L / hour. The GHSV at this time was 10,000. The outlet gas of the evaporator was supplied to the reactor as it was, and the dehydration reaction was carried out in the reactor for 8 hours. The outlet gas for 1 to 8 hours was collected by cooling to obtain a reaction solution. When the reaction solution was analyzed, the conversion of 3HP was 95 mol%, the yield of acrylic acid was 92 mol%, and the selectivity for acrylic acid was 97 mol%. Slight coloration was observed on the catalyst extracted after the reaction, suggesting that coking had occurred. The catalyst was heated in air using a differential thermobalance, and the amount of coke on the catalyst was calculated from the weight reduction, and it was 2.7% by mass.

Example 2
(Preparation of catalyst)
Except for changing lithium sulfate monohydrate 2.1 g to 2.8 g of sodium nitrate in Example 1, a catalyst having a composition excluding oxygen and consisting of Na ₁ Si ₁₀ was obtained.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 98 mol%, the yield of acrylic acid was 96 mol%, and the selectivity of acrylic acid was 98 mol%. The amount of coke on the catalyst was 2.3% by mass.

Example 3
(Preparation of catalyst)
Except for changing 2.1 g of lithium sulfate monohydrate to 2.9 g of potassium sulfate in Example 1, a catalyst having a composition excluding oxygen and consisting of K ₁ Si ₁₀ was obtained.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 98 mol%, the yield of acrylic acid was 95 mol%, and the selectivity for acrylic acid was 97 mol%. The amount of coke on the catalyst was 2.6% by mass.

Example 4
(Preparation of catalyst)
In Example 1, except that 2.1 g of lithium sulfate monohydrate was changed to 3.3 g of cesium nitrate, a catalyst whose composition excluding oxygen was Cs ₁ Si ₁₀ was obtained.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion rate of 3HP was 100 mol%, the yield of acrylic acid was 98 mol%, and the selectivity of acrylic acid was 98 mol%. The amount of coke on the catalyst was 2.6% by mass.

Example 5
(Preparation of catalyst)
In the first embodiment, in the same manner except for changing the lithium sulfate monohydrate 2.1g sodium nitrate 2.8g and diammonium hydrogen phosphate 1.4g, composition excluding oxygen _Na 1 _{P 0. A} catalyst composed of ₃ Si ₁₀ was obtained.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion rate of 3HP was 100 mol%, the yield of acrylic acid was 98 mol%, and the selectivity of acrylic acid was 98 mol%. The amount of coke on the catalyst was 2.4% by mass.

Example 6
(Preparation of catalyst)
In Example 1 above, except that 2.1 g of lithium sulfate monohydrate was changed to 3.3 g of cesium nitrate and 0.28 g of boric acid, the composition excluding oxygen was Cs ₁ B _0.2 Si ₁₀ A catalyst consisting of
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion rate of 3HP was 95 mol%, the yield of acrylic acid was 92 mol%, and the selectivity for acrylic acid was 97 mol%. The amount of coke on the catalyst was 2.6% by mass.

Example 7
(Preparation of catalyst)
In Example 1, except that 2.1 g of lithium sulfate monohydrate was changed to 2.0 g of magnesium sulfate, a catalyst in which the composition excluding oxygen was Mg ₁ Si ₂₀ was obtained.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 90 mol%, the yield of acrylic acid was 87 mol%, and the selectivity for acrylic acid was 97 mol%. The amount of coke on the catalyst was 1.9% by mass.

Example 8
(Preparation of catalyst)
In Example 1, except that 2.1 g of lithium sulfate monohydrate was changed to 3.9 g of calcium nitrate tetrahydrate, a catalyst having a composition excluding oxygen and consisting of Ca ₁ Si ₂₀ was obtained. .
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 92 mol%, the yield of acrylic acid was 90 mol%, and the selectivity for acrylic acid was 98 mol%. The amount of coke on the catalyst was 2.2% by mass.

Example 9
(Preparation of catalyst)
In Example 1 above, except that 2.1 g of lithium sulfate monohydrate was changed to 5.2 g of barium hydroxide octahydrate, a catalyst in which the composition excluding oxygen was Ba ₁ Si ₂₀ was obtained. It was.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 92 mol%, the yield of acrylic acid was 89 mol%, and the selectivity for acrylic acid was 97 mol%. The amount of coke on the catalyst was 2.4% by mass.

Example 10
(Preparation of catalyst)
In Example 1 above, except that 2.1 g of lithium sulfate monohydrate was changed to 0.67 g of potassium nitrate and 2.7 g of cesium carbonate, the composition excluding oxygen was changed from Cs ₁ K _0.4 Si _20. The resulting catalyst was obtained.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 100 mol%, the yield of acrylic acid was 95 mol%, and the selectivity for acrylic acid was 95 mol%. The amount of coke on the catalyst was 1.6% by mass.

Example 11
(Preparation of catalyst)
After dissolving 1.0 g of potassium sulfate in 100 g of water and adding 20 g of aluminum oxide while heating and stirring at 90 ° C., the solution was concentrated to dryness and then dried at 120 ° C. for 20 hours in an air atmosphere. The obtained solid was coarsely pulverized and further calcined in air at 500 ° C. for 2 hours to obtain a catalyst whose composition excluding oxygen was K ₁ Al ₂₀ . The obtained catalyst was crushed to 10 to 24 mesh and used for dehydration reaction.
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 98 mol%, the yield of acrylic acid was 96 mol%, and the selectivity for acrylic acid was 94 mol%. The amount of coke on the catalyst was 2.3% by mass.

Example 12
(Preparation of catalyst)
Spherical ZSM-5 type zeolite (proton type, silicon / aluminum = 100/1) was synthesized according to the method of JP2009-190915A. Cesium nitrate (1.0 g) was dissolved in water (100 g), 20 g of the zeolite was added at room temperature and stirred for 3 hours, filtered to separate the zeolite, added again to the aqueous cesium nitrate solution, stirred at room temperature for 3 hours and filtered. The obtained cesium-supported zeolite was dried in an air atmosphere at 120 ° C. for 20 hours. Moreover by baking for 2 hours at 500 ° C. in air, the composition excluding oxygen was obtained a catalyst composed of _Cs 1 _Al 1.4 _{Si 143.}
(Dehydration reaction)
A dehydration reaction was performed in the same manner as in Example 1 using the above catalyst. The conversion of 3HP was 100 mol%, the yield of acrylic acid was 99 mol%, and the selectivity for acrylic acid was 99 mol%. The amount of coke on the catalyst was 2.4% by mass.

Comparative Example 1
In the dehydration step of Example 1, a dehydration reaction was performed in the same manner except that the catalyst was changed to silicon oxide. The conversion of 3HP was 43 mol%, the yield of acrylic acid was 39 mol%, and the selectivity for acrylic acid was 91 mol%. The amount of coke on the catalyst was 1.9% by mass. Compared with the catalyst of an Example, activity was remarkably inferior and the conversion rate of 3HP was very low. Since the acrylic acid yield is low, the value of coke amount on the catalyst per unit yield of acrylic acid [coke amount on the catalyst (mass%)] / [acrylic acid yield (mol%)] is 0.05. Compared to 0.02 in the case of Example 1, it is twice or more, and for the same acrylic acid production, it is suggested that the amount of coke produced in Comparative Example 1 is twice or more compared to Example 1. .

Comparative Example 2
In the dehydration step of Example 1, a dehydration reaction was performed in the same manner except that the catalyst was changed to titanium oxide. The conversion rate of 3HP was 97 mol%, the yield of acrylic acid was 88 mol%, and the selectivity for acrylic acid was 91 mol%. The amount of coke on the catalyst was 7.6% by mass. Compared with the catalyst of an Example, the selectivity of acrylic acid was low and the amount of coke on a catalyst was remarkably large.

Comparative Example 3
In the dehydration step of Example 1, a dehydration reaction was performed in the same manner except that the catalyst was changed to zirconium oxide. The conversion of 3HP was 98 mol%, the yield of acrylic acid was 87 mol%, and the selectivity for acrylic acid was 89 mol%. The amount of coke on the catalyst was 9.3% by mass. Compared with the catalyst of an Example, the selectivity of acrylic acid was low and the amount of coke on a catalyst was remarkably large.

Example 13
(Preparation of catalyst)
Dissolve 1.7 g of potassium nitrate and 1.1 g of diammonium hydrogen phosphate in 100 g of water, add 20 g of silicon oxide with heating and stirring at 90 ° C., concentrate to dryness, and then dry at 120 ° C. for 20 hours in an air atmosphere. did. The obtained solid was coarsely pulverized and further calcined in air at 500 ° C. for 2 hours to obtain a catalyst whose composition excluding oxygen was K ₁ P _0.5 Si ₂₀ . The obtained catalyst was crushed to 10 to 24 mesh and used for dehydration reaction.
(Dehydration reaction)
A stainless steel tube having an inner diameter of 10 mm was filled with 1.5 mm Dixon packing made of stainless steel as an evaporation layer, and the evaporator was installed in an electric furnace. Further, a stainless steel tube having an inner diameter of 10 mm was filled with 2.2 ml of the above catalyst, and installed in an electric furnace to prepare a reactor. The outlet of the evaporator and the inlet of the reactor were connected with a stainless steel tube so that the surroundings could be heated with an electric heater.
Moreover, the temperature in an evaporator was 275 degreeC, the temperature in a reactor was 300 degreeC, and the 12 mass% aqueous solution of 3-hydroxypropionic acid was supplied to the upper part of the evaporator at the speed | rate of 33.5g / h. At the same time, nitrogen gas was flowed at a rate of 6 L / hour. The GHSV at this time was 20000. The outlet gas of the evaporator was supplied to the reactor as it was, and the dehydration reaction was carried out in the reactor for 24 hours. The exit gas for 1-2 hours and 23-24 hours was collected by cooling to obtain a reaction solution. When the reaction solution was analyzed, the conversion rate of 3HP in 1 to 2 hours was 88 mol%, the yield of acrylic acid was 86 mol%, the conversion rate of 3HP in 23 to 24 hours was 82 mol%, The yield was 81 mol%, and a decrease in catalyst activity was observed.
Therefore, the temperature of the reactor was raised to 450 ° C., and a mixed gas of 2 volume% oxygen and 98 volume% nitrogen was allowed to flow at 6 L / hour for 12 hours, and then air was allowed to flow at 6 L / hour for 12 hours to deposit on the catalyst. The coke was burned to regenerate the catalyst.
Thereafter, the reaction was carried out again under the above reaction conditions. As a result, the conversion rate of 3HP in 1 to 2 hours was 88 mol%, the yield of acrylic acid was 87 mol%, and the conversion rate of 3HP in 23 to 24 hours was 81 mol%. The yield of acrylic acid was 80 mol%, almost the same reaction result as the first time.

In this way, by using a specific oxide containing an alkali metal element and / or an alkaline earth metal element as a dehydration catalyst, dehydration reaction of 3-hydroxycarboxylic acid or its ester (meth) acrylic acid or its By using the method for producing (meth) acrylic acid or an ester thereof according to the present invention to produce an ester, side reactions are suppressed, and the conversion rate of 3-hydroxycarboxylic acid or an ester thereof and (meth) acrylic acid or an ester thereof Efficient production of high-purity (meth) acrylic acid or its ester by improving ester selectivity and reducing coking on the catalyst to suppress catalyst activity drop and reactor blockage The mechanism of action that can be done is considered to be the same.
Therefore, it can be said from the results of the above-described embodiments that the present invention can be applied in the entire technical scope of the present invention and in various forms disclosed in the present specification, and can exhibit advantageous effects.

Claims (2)

A method for producing (meth) acrylic acid or an ester thereof from a raw material composition containing 3-hydroxycarboxylic acid or an ester thereof,
The production method includes a dehydration step of producing (meth) acrylic acid or an ester thereof by dehydrating the 3-hydroxycarboxylic acid or an ester thereof,
The dehydration step is performed using a dehydration catalyst, and
The dehydration catalyst has the following general formula (1):
M _a X _b Y _c O _d (1)
Wherein M is at least one element selected from the group consisting of alkali metals and alkaline earth metals; X is at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium; Y is boron and phosphorus At least one element selected from the group consisting of: O represents oxygen, a is 1, b is a number from 1 to 300, c is a number from 0 to 0.8, d is a value of a, b, c and various configurations. (The value is determined by the bonding state of the element.)
(Meth) acrylic acid or its ester manufacturing method characterized by being the oxide represented by these. The method according to claim 1, wherein the 3-hydroxycarboxylic acid is 3-hydroxypropionic acid.