JP2014189513A - Production method of acrylic acid and/or acrylic acid ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for improving quality of acrylic acid and/or an acrylic acid ester which are synthesized by using lactic acid or a lactic acid ester as a raw material by removing 2,3-pentanedione therefrom.SOLUTION: A production method of acrylic acid and/or an acrylic acid ester includes a step to separate acrylic acid and/or the acrylic acid ester from 2,3-pentanedione, in the production method of acrylic acid and/or the acrylic acid ester from lactic acid or a lactic acid ester.

Description

  The present invention relates to a method for producing acrylic acid and / or acrylic ester. More specifically, the present invention relates to a method for producing high-purity acrylic acid and / or acrylic ester using biomass such as lactic acid as a raw material.

  Polyacrylic acid (salt) water-absorbing resin using acrylic acid and / or its salt as a monomer is used for absorbent articles such as paper diapers and sanitary napkins, agricultural and horticultural water retention agents, It is widely used industrially for water-stopping materials.

  The current method for producing acrylic acid is generally a method in which propylene is oxidized in air, but this method converts propylene to acrolein by catalytic gas phase oxidation, which is converted to acrylic acid in catalytic gas phase oxidation, In this production method, the gaseous reaction mixture is absorbed in water, and the crude acrylic acid obtained by distilling the aqueous acrylic acid solution thus obtained is further purified by distillation or crystallization.

  However, the production method uses propylene obtained by refining crude oil, which is a fossil resource, as a raw material, and a production method that can reduce raw material costs and environmental burden in view of problems such as recent rise in crude oil prices and global warming. An alternative to is desired.

  As a production method that can replace such a current production method, a synthesis method from a carbon-neutral biomass material has been actively studied, and one of them is intramolecular dehydration from lactic acid (LA) or lactic acid ester (LE). There is a method of obtaining acrylic acid (AA) or acrylic ester (AE) by reaction. This method is generally a method of obtaining acrylic acid (AA) or acrylic acid ester (AE) by intramolecular dehydration reaction of lactic acid or lactic acid ester on a solid catalyst such as zeolite under a high temperature condition of 300 ° C. or higher (non-patent document). Reference 1).

  However, in this dehydration reaction of lactic acid or lactic acid ester, as shown in FIG. 1 of Non-Patent Document 2, in addition to the dehydration reaction, decarboxylation reaction, hydrogen reduction reaction, condensation reaction, dimerization reaction, dehydrogenation reaction, etc. As a result, acetaldehyde, propionic acid, lactide, and 2,3-pentanedione can be by-produced as products in addition to acrylic acid (Non-patent Document 2). In addition, a production method of α, β-unsaturated carboxylic acid by a gas phase dehydration method using a solid catalyst has been disclosed so far (see Patent Document 1), but there is no production example of acrylic acid on an industrial scale. The technology for separating and purifying impurities produced in the manufacturing process has not been established.

Japanese Patent Laid-Open No. 3-167157

Kochi University, Ayumu Onda, "Conversion of biomass-derived compounds by zeolite catalyst", CM Publishing, February 2013, p. 26-29 Catalyst Reviews. , 51 (2009) 293-324.

  Of the by-products in such a method for producing acrylic acid, 2,3-pentanedione is not produced by the conventional propylene method, but this substance is yellow and has a peculiar odor. There is a problem of deteriorating the quality of certain acrylic acids or acrylic esters. In particular, acrylic acid is used as a raw material for a super absorbent resin (SAP) used in disposable diapers, sanitary products, and the like, which may cause coloring and off-flavors of those products.

  Accordingly, an object of the present invention is to provide a method for removing 2,3-pentanedione from acrylic acid and / or lactic acid ester synthesized using lactic acid or lactic acid ester as a raw material to enhance their quality.

  In view of the above problems, the present inventors conducted extensive research. As a result, by incorporating the step of separating acrylic acid and its ester and 2,3-pentanedione into the step of producing acrylic acid and / or acrylic ester from lactic acid and / or lactic acid ester, 2,3-pentanedione Has been found to be almost completely separable from acrylic acid and / or acrylate esters, and the present invention has been completed.

  That is, the present invention includes a step of separating acrylic acid and / or acrylic ester and 2,3-pentanedione in a method for producing acrylic acid and / or acrylic ester from lactic acid and / or lactic ester. A method for producing acrylic acid and / or acrylic ester.

  According to the present invention, 2,3-pentanedione can be removed from acrylic acid synthesized using lactic acid or its ester as a raw material and its ester to improve their quality.

  In the method for producing acrylic acid using lactic acid ester as a raw material, acrylic acid produced by preventing accumulation of 2,3-pentanedione in the process by recycling unreacted crude acrylic acid ester in the hydrolysis process is used. The quality of the acid can be increased.

It is a manufacturing flowchart concerning the method of manufacturing acrylic acid using lactic acid as a raw material according to an embodiment of the present invention. It is a manufacturing flowchart concerning the method of manufacturing acrylic acid ester and acrylic acid simultaneously from lactic acid ester as a raw material according to another embodiment of the present invention. It is a manufacturing flowchart concerning the method of manufacturing only acrylic acid using lactic acid ester as a raw material according to another embodiment of the present invention.

  The present invention relates to an acrylic acid comprising a step of separating acrylic acid and / or an acrylic ester and 2,3-pendandione in a method for producing acrylic acid and / or an acrylic ester from lactic acid and / or a lactic ester. And / or a method for producing an acrylate ester. By setting it as the manufacturing method including such a process, 2, 3- pentanedione can be removed from acrylic acid and its ester synthesize | combined by using lactic acid or its ester as a raw material, and those quality can be improved.

  In the following, referring to FIGS. 1 to 3, an outline of a preferred embodiment of a method for producing acrylic acid using lactic acid as a raw material and a method for producing acrylic acid and / or acrylic ester using a lactic acid ester as a raw material will be outlined. explain. However, the present invention is not limited to this embodiment.

<Method for producing acrylic acid using lactic acid as a raw material>
About the method for producing acrylic acid using lactic acid as a raw material which is one embodiment of the present invention, a step of subjecting lactic acid to a dehydration reaction to obtain a dehydration reaction product containing acrylic acid, water, and 2,3-pentanedione (A- 1) and the process (B-1) of removing 2,3-pentanedione contained in the dehydration reaction product will be described.

  FIG. 1 is a production flowchart according to a method for producing acrylic acid by vapor phase dehydration reaction using lactic acid as a raw material according to one embodiment of the present invention. In FIG. 1, the lactic acid aqueous solution is heated and vaporized in the dehydration step (A-1), and after vapor phase dehydration reaction is generated through a fixed bed reactor filled with a solid catalyst to produce acrylic acid, the reaction gas is cooled. Liquefy. In the 2,3-pentanedione removal step (B-1), the reaction product solution is subjected to a distillation operation, and water and 2,3-pentanedione are distilled off from the top of the tower and discarded, and crude acrylic acid is removed from the bottom of the tower. Recover. Crude acrylic acid is purified by a general method such as distillation or crystallization to obtain purified acrylic acid.

[Dehydration step (A-1)]
The dehydration step (A-1) is a step of subjecting lactic acid to a dehydration reaction in a method for producing acrylic acid using lactic acid as a raw material to obtain a dehydration reaction product containing acrylic acid, water, and 2,3-pentanedione. .

(Lactic acid)
The lactic acid used for the reaction can be either a general production method produced by fermentation or a chemical method. Lactic acid is usually distributed in the form of an aqueous solution, and may be used as it is, may be further diluted with water, or may be used by appropriately concentrating after removing moisture using an operation such as evaporation. Good. As water used for the dilution, lactic acid diluted with ion exchange water, pure water, normal tap water or the like may be used, or waste water generated in the production process may be recycled. The concentration of lactic acid is preferably 10% by mass or more, more preferably 30% by mass or more from the viewpoint of process efficiency. In order to obtain a high reaction yield, the concentration of lactic acid is preferably 90% by mass or less, more preferably 80% by mass or less. In addition to the lactic acid monomer, the lactic acid used in the reaction may contain a condensate of lactic acid such as an oligomer of lactic acid or lactide. Here, the concentration of lactic acid refers to the concentration of lactic acid monomer and lactic acid. This is a concentration containing an oligomer or lactide, which is a concentration determined by the method described in JIS K8726.

(Reactor)
The reaction apparatus used for the dehydration reaction of lactic acid in the present invention is not particularly limited, and examples thereof include a stirring reactor, a fixed bed type, a fluidized bed type, and a spouted bed type, and preferably a fixed bed type.

  The fixed bed reactor in the present invention includes a reaction tube filled with a solid catalyst, and dehydrates lactic acid by a gas phase contact reaction while allowing a volatile component of a lactic acid aqueous solution as a raw material to pass through the reaction tube. Acrylic acid is obtained.

  The fixed bed reactor also includes a raw material gas inlet provided at the reactor inlet, a product outlet provided at the reactor outlet, and a heat medium for heating or removing heat from the reaction tube. And a heat medium outlet for discharging the heat medium from the reactor. Further, the reaction tube may be heated with an electric heater or the like instead of the heat medium.

  The reaction tube provided in the fixed bed reactor of the present invention may be a single reaction tube or a plurality of reaction tubes. When a plurality of reaction tubes are arranged, the reaction tubes are usually metal tubes having substantially the same shape.

  The reaction tube may be coiled or the like, but usually a straight straight tube is used. The straight pipe may be either a horizontal arrangement or a vertical arrangement, but is usually a vertical type that is arranged in the vertical direction and allows the source gas to pass in the vertical direction.

  The reactor can be used not only when lactic acid is used as a raw material but also when lactic acid ester is used.

(Solid catalyst)
The catalyst used for the reaction is not particularly limited, and examples thereof include sulfate, phosphate, nitrate, alumina, silica, titania, zeolite, and hydroxyapatite.

Examples of the sulfate include Na ₂ SO ₄ , K ₂ SO ₄ , CaSO ₄ , Al ₂ (SO ₄ ) _{3 and the} like. Examples of phosphates include Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH ₂ PO ₄ , CaHPO ₄ , Ca ₃ (PO ₄ ) ₂ , AlPO ₄ , CaH. such as _{2 P 2 O 7, Ca 2} P 2 O 7 and the like. Examples of nitrates include NaNO ₃ , KNO ₃ , and Ca (NO ₃ ) ₂ .

  Examples of the zeolite include ZSM, ZSM-12, ZSM-11, X zeolite, Ti-MWW, Ti-MCM-41, SAPO-34, SAPO-11, NaX zeolite, NaA zeolite, MFI, MCM-68, and MCM. -22, LTA zeolite, ETS-10, BEA zeolite, Al-MCM-41, organic zeolite, zeolite L, zeolite A, mordenite, faujasite, clinobutyrolite, beta zeolite, silicalite, Y zeolite, ZSM-5 Is mentioned. An example of silicalite is silicalite-1. Examples of Y zeolite include HY zeolite, NaY zeolite, and USY zeolite. Examples of ZSM-5 include HZSM-5, Cu-ZSM-5, Fe / ZSM-5, and NaZSM-5.

Among these catalysts, phosphate is preferable, and Ca ₃ (PO ₄ ) ₂ or Ca ₂ P ₂ O ₇ and a mixture thereof are particularly preferable.

  These catalysts may be used by being supported on a carrier. Examples of the carrier include silica, diatomaceous earth, alumina, silica alumina, silica magnesia, zirconia, titania, magnesia, niobia, ceria, zeolite, silicon carbide, carbide, and the like, and titania, silica, zirconia, or alumina is preferable. Among these, it may be carried on one type of carrier, or may be carried on a carrier composed of two or more composites or mixtures. Moreover, these catalysts may contain metals, such as Cs, Ba, Y, La, and Ce, as an additive.

  These catalysts may be powders, crushed bodies, or molded bodies. The shape of the molded body is not limited, and examples thereof include a spherical shape, a cylinder type, a ring type, and a honeycomb type.

  The solid catalyst can be used not only when lactic acid is used as a raw material but also when a lactic acid ester is used.

(Reaction conditions)
The reaction temperature may be appropriately determined according to the catalyst used and the conversion and selectivity of the reaction, but in order to obtain a sufficient reaction rate, it is usually 250 ° C. or higher, more preferably 300 ° C. or higher, more preferably 350 ° C. or higher. Further, in order to suppress the side reaction and sufficiently obtain the target compound selectivity, the reaction temperature is 500 ° C. or lower, more preferably 450 ° C. or lower, and further preferably 400 ° C. or lower.

  Although the pressure in the reactor is not particularly limited, it is 30 kPa or more, more preferably 60 kPa or more from the viewpoint of equipment required for decompression and cooling of the reaction gas. Further, from the viewpoint of materials required for high pressure equipment and reactors, 200 kPa or less, more preferably 150 kPa or less is preferable.

  In the case of using a carrier gas, an inert gas can be used, preferably nitrogen, argon or helium, and more preferably nitrogen from an economical viewpoint. Also, water vapor can be used as the carrier gas. In this case, water vapor obtained by vaporizing water in the raw lactic acid aqueous solution can be used as it is, or water vapor can be newly added.

The flow rate of the reaction gas may be appropriately adjusted in consideration of the raw material concentration, the amount of carrier gas, the performance of the catalyst, the productivity, and the like. ^-1, preferably 100～10000H ^-1, more preferably 150～6000H ^-1.

  The above reaction conditions can be used not only when lactic acid is used as a raw material but also when a lactic acid ester is used.

[2,3-pentanedione removal step (B-1)]
In the 2,3-pentanedione removal step (B-1), the dehydration reaction product containing acrylic acid, water, and 2,3-pentanedione obtained in the dehydration step (A-1) is treated with water and 2 , 3-pentanedione and a phase containing crude acrylic acid. The separation operation is not particularly limited, and examples thereof include distillation, membrane separation, extraction, and crystallization, and distillation is preferred.

(distillation)
The distillation step in the present embodiment includes a step of collecting a gaseous dehydration reaction product containing acrylic acid, water, and 2,3-pentanedione to obtain a reaction product solution, water from the reaction product solution, and In this step, 2,3-pentanedione is removed to obtain crude acrylic acid.

  Distillation towers used for distillation operations include collection towers, absorption towers, dehydration towers, azeotropic dehydration towers, low boiling point substance separation towers, high boiling point substance separation towers, purification towers, thin film evaporators, etc. Widely included are devices used to separate the components to be separated.

  As an operation, first, a condensate of the acrylic acid-containing gas is obtained. This operation may be performed by supplying an acrylic acid-containing gas to the acrylic acid collection tower. This step may involve a step of collecting acrylic acid contained in the gas obtained in the reaction step with an aqueous collection solvent. Any of the conventionally known acrylic acid collection steps can be applied to the collection conditions such as the gas component composition of the reaction gas, the composition of the aqueous collection solvent, and the collection temperature. When unreacted lactic acid is contained in the acrylic acid-containing gas, the acrylic acid-containing gas may be supplied to the acrylic acid collection tower after the lactic acid is removed by distillation or diffusion. Further, the gas may be cooled and then supplied to the collection tower. A lower gas temperature is preferable in terms of improving the collection efficiency.

  As the collection tower, a known collection tower such as a plate tower, a packed tower, a wet wall tower, or a spray tower can be used. Such a collection tower is usually preferably a plate tower or a packed tower. In the case of packed towers, the interior has a large surface area and is filled regularly or irregularly with an air-permeable packing, and gas-liquid contact is made on the surface of the packed bed packed with packing. Is done.

  In the collection tower, an acrylic acid-containing gas is introduced into the collection tower, while a collection solvent that absorbs acrylic acid is introduced into the tower from the upper portion of the collection tower and is brought into countercurrent contact with the gas to obtain acrylic acid. To absorb.

  An aqueous collection solvent is used as the collection solvent to be supplied. It is inexpensive and can advantageously reuse wastewater discharged from the acrylic acid production process. Such an aqueous collection solvent may contain at least 80 to 100% by mass of water, for example, 0.1 to 5.0% by mass of acrylic acid, 0.1 to 10% by mass of acetic acid, and 80 to 99.99% of water. There is 8% by mass. The collection solvent may be used after adjusting the composition described above, for example, an acrylic acid collection tower using, as an acrylic acid collection solvent, an aqueous phase in an oil-water separator attached to an azeotropic dehydration tower. It can also be used in circulation.

The trapping solvent has a higher trapping rate when the solvent temperature is lower, and the solvent temperature is preferably supplied at a constant temperature in the range of 0 to 35 ° C, particularly 5 to 30 ° C. Further, the solvent amount is the amount of feed gas ^{(m 3)} solvent amount relative to (L) liquid-to-gas ratio represented by ratio 2~15L / ^{m 3,} preferably 3~12L / ^{m 3,} more preferably 5 to 10 L / It is set to be m ^3. When the mass ratio of acrylic acid and water is about 50:50, the polymerization of acrylic acid is most likely to occur, and acrylic acid can be efficiently collected while preventing polymerization in the above range.

  The collection solvent includes N-oxyl compounds, phenolic compounds, manganese salts such as manganese acetate, dialkyldithiocarbamic acid copper salts such as copper dibutylthiocarbamate, nitroso to prevent polymerization of polymerizable substances such as acrylic acid. You may contain 1 or more types of compounds chosen from the group which consists of a compound, an amine compound, and phenothiazine.

  The amount of the polymerization inhibitor used is appropriately adjusted according to the operating conditions, and is not particularly limited. However, the total amount of the polymerization inhibitor used is preferably 3 to 3500 ppm (mass basis) based on the mass of acrylic acid in the reaction gas to be collected.

  The polymerization inhibitor may be administered as a solution, that is, a polymerization inhibitor-containing solution. The supply location and administration method of the polymerization inhibitor-containing solution are not particularly limited, and the polymerization inhibitor-containing solution may be supplied from any of the collection towers as long as it is other than the raw material supply stage of the distillation tower and other than the reflux liquid supply stage.

  The conditions of the collection tower differ depending on the temperature of the acrylic acid-containing gas supplied here, the supply amount per unit time, the volume of the collection tower, etc., but generally the top temperature of the collection tower is 40 to 90 ° C. Range. If it is lower than 40 ° C., it is disadvantageous because it requires equipment costs and cooling energy for cooling. Moreover, since the condensation of substances having a boiling point lower than that of acrylic acid increases, it causes a decrease in the acrylic acid purity of the collection tower bottom liquid. On the other hand, when it exceeds 90 ° C., the loss of acrylic acid from the top of the collection tower increases, and the product yield may be reduced.

  The exhaust gas from the top of the column may be circulated to the reactor, and dilution gas and unreacted raw material components can be used effectively.

  The tower bottom liquid of the collection tower may be circulated to the collection tower after the tower bottom liquid is cooled by a cooler attached to the tower bottom to increase the acrylic acid concentration in the tower bottom liquid. In general, in the bottom liquid of the collection tower, that is, the reaction product solution, in addition to acrylic acid, additives such as lactic acid and other by-products remaining in an unreacted state and a polymerization inhibitor are present.

  In the present invention, the reaction product solution may then be led to a distillation column and distilled. The conditions for the distillation operation such as the supply rate of the reaction product solution, the distillation rate of the distillate from the top of the column, and the reflux ratio may be appropriately adjusted depending on the separation ability and processing capability of the distillation column used. . This distillation operation may be performed by azeotropic distillation with the addition of an azeotropic solvent. In the present application, after the step of obtaining the reaction product solution, it is preferable to perform the next step after the tank and / or the cooler is installed to cool the transition product of the next step. For example, if necessary, the reaction product solution is supplied to a distillation column to remove low-boiling substances including 2,3-pentanedione, and then the bottom liquid is transferred to a cooler by a pump, and the reaction product cooled here The physical solution is stored in a tank. This is because the liquid can be reliably cooled by cooling before transferring to a substance tank having a lower boiling point than acrylic acid, the residence time in the high temperature part can be reduced, and the amount of oligomers generated can be suppressed. . In addition, the low boiling point substance in this application means a substance having a lower boiling point than acrylic acid. The bottom liquid of the collection tower may be transferred to the tank without passing through the distillation tower, then transferred to the cooler by a pump, and then circulated to the tank and the liquid may be transferred to the next step. Examples of the cooler include conventionally known multi-tube heat exchangers, plate heat exchangers, and spiral heat exchangers. Low-boiling substances containing 2,3-pentanedione that can be removed by a distillation tower can be removed there by providing a dehydration tower separately from the distillation tower. Material separation may be performed. In this respect, the reaction product solution in the present application widely includes acrylic acid containing water before moving to a dehydration tower or a low-boiling-point material separation tower, and collects the tower bottom liquid and the tower bottom after distillation. Applicable to liquids. In addition, it is preferable that the cooling temperature of the reaction product solution in a tank shall be 20-50 degreeC. Next, the reaction product solution in the tank is supplied to the distillation column.

  As the distillation tower, known towers such as a plate tower, a packed tower, a wet wall tower, and a spray tower can be used. Such a dehydration tower is usually preferably a plate tower or a packed tower, like the above collection tower. In addition, the preferable theoretical plate number of the distillation column is 5 or more and 100 or less, more preferably 10 or more and 50 or less, from the viewpoint of both separation ability and equipment cost.

As the azeotropic solvent used when the distillation operation is performed by azeotropic distillation, a solvent containing at least one selected from heptane, dimethylcyclohexane, ethylcyclohexane, toluene, ethylbenzene, chlorobenzene, xylene and a mixture thereof;
Diethyl ketone, diisopropyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl t-butyl ketone, n-propyl acetate, n-butyl acetate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acrylate, acrylic acid n- A solvent comprising at least one selected from the group consisting of propyl, allyl acetate, isopropenyl acetate, vinyl propionate, propyl propionate, methyl crotonate, methyl valerate, ethyl butyrate, dibutyl ether, and mixtures thereof; and A solvent containing at least one selected from heptane, dimethylcyclohexane, ethylcyclohexane, toluene, ethylbenzene, chlorobenzene, xylene and mixtures thereof; diethyl ketone, diisopropyl ketone, methyl Propyl ketone, methyl isobutyl ketone, methyl-t-butyl ketone, n-propyl acetate, n-butyl acetate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acrylate, n-propyl acrylate, allyl acetate, isopropenyl acetate And a mixed solvent with a solvent containing at least one selected from the group consisting of vinyl propionate, propyl propionate, methyl crotonic acid, methyl valerate, ethyl butyrate, dibutyl ether, and mixtures thereof.

  More preferably, a solvent containing at least one selected from heptane, toluene and mixtures thereof; at least one selected from ethyl methacrylate, methyl isobutyl ketone, n-propyl acrylate, n-butyl acetate and mixtures thereof. A solvent containing seeds; and a solvent containing at least one selected from heptane, toluene and mixtures thereof, and selected from ethyl methacrylate, methyl isobutyl ketone, n-propyl acrylate, n-butyl acetate and mixtures thereof And a solvent containing at least one selected from the above.

  Further, since the amount of the azeotropic solvent used is determined by the water content contained in the reaction product solution supplied to the azeotropic dehydration tower and the type of the azeotropic solvent used, it cannot be uniquely defined. , And can be used at a conventionally known ratio used for azeotropic use. In particular, from the viewpoint of preventing the polymerization of acrylic acid, a larger amount of azeotropic solvent is preferable, but a larger amount is disadvantageous because a large amount of distillation energy is required.

  The temperature at the top of the distillation column is the amount of water in the reaction product solution supplied, the amount of mixed by-products, the amount of supply liquid per unit time, the supply liquid temperature, the desired degree of dehydration, and other components to be separated. The preferred conditions can be selected depending on the type and content of these, the type of distillation column introduced into the purification step of acrylic acid, and the like. Also, an azeotropic dehydration tower is provided with an oil / water separator, and a distillate from the top of the tower is introduced into the azeotropic dehydration tower to separate it into an oil phase (azeotropic solvent phase) and an aqueous phase. It is efficient to reflux to the boiling dehydration tower at a reflux ratio of 0.5 to 10 and circulate the water phase to the collection tower and use it as a collection solvent.

  In the distillation column, a polymerization inhibitor may be appropriately added for the purpose of preventing undesired polymerization of acrylic acid. As the polymerization inhibitor, any one described in the section of the collection tower can be used alone or in combination of two or more.

  In the present invention, the polymerization inhibitor may be supplied together with acrylic acid. In particular, water and solvent evaporate above the supply stage of the distillation column, but acrylic acid does not evaporate and moves to the bottom of the column. Therefore, if acrylic acid is present, the polymerization inhibitor is also accompanied by the polymerization inhibitor. Precipitation can be prevented and effective. In addition, when the thermal decomposition thing of an acrylic acid oligomer mentioned later as acrylic acid is used, it will become an effective use of acrylic acid and can improve manufacturing efficiency. In particular, when it is supplied to a distillation column, it is preferable in terms of improving the quality of the product and preventing precipitation of the polymerization inhibitor.

  Although the low boiling point material containing water and 2,3-pentanedione contained in the reaction product solution is removed by the distillation treatment, the water separation step and the low boiling point material separation step may be performed separately. In general, after the dehydration treatment, a high boiling point substance separation step and other conventionally known purification methods can be used alone or in combination. Therefore, not limited to the distillation method, 2,3-pentanedione may be removed by crystallization of acrylic acid. Since the selection range of the 2,3-pentanedione removal step is wide, in the present invention, a product obtained by removing low-boiling substances containing water and 2,3-pentanedione from the reaction product solution is referred to as crude acrylic acid. Is transferred to a high boiling point material separation step.

  The crude acrylic acid may be cooled by placing it in a cooler or tank between the dehydration step and / or the low boiling point material separation step containing 2,3-pentanedione and the high boiling point material separation step. This is because the residence time in the high temperature part can be reduced and the amount of oligomers produced can be suppressed. In addition, it is preferable that the cooling temperature of the crude acrylic acid in a tank shall be 20-50 degreeC. As the cooler, a conventionally known multi-tube heat exchanger, plate heat exchanger, spiral heat exchanger, or the like can be used. Next, the crude acrylic acid in the tank is supplied to the high boiling point material separation tower. The high boiling point material separation tower is a process in which the treatment liquid is heated to distill acrylic acid from the top of the distillation tower, and it is preferable that the temperature of the feed liquid is high in terms of thermal efficiency. However, the higher the temperature of crude acrylic acid, the higher the oligomer formation rate and the higher the risk of polymerization, or the easier it is to generate polymer in the high-boiling point separation tower, and the final acrylic acid yield decreases. In some cases, continuous operation may be hindered by the generation of polymer. On the other hand, when the temperature is lower than 20 ° C., it approaches the freezing point, and the risk of freezing and the heating amount in the high boiling point substance removing step increase, which is disadvantageous. Therefore, in the present invention, the final production rate is comparatively weighed based on the generation amount of the polymer and the thermal efficiency, and the processing liquid is cooled between the next steps. In particular, it is preferable to cool the treatment liquid between the dehydration treatment and the high boiling point material treatment in terms of improving the yield.

  As the high boiling point substance separation tower, known towers such as a plate tower, a packed tower, a wet wall tower, and a spray tower can be used. Such a high boiling point substance separation tower is usually a plate tower or a packed tower, like the azeotropic dehydration tower. Further, the number of theoretical plates is preferably 3 to 50, more preferably 5 to 30.

  The distillation conditions of the high boiling point material separation tower can be distilled under conventionally known distillation conditions.

  Moreover, it is preferable to add a polymerization inhibitor as appropriate in the high-boiling-point material separation tower for the purpose of preventing undesired polymerization of acrylic acid as in the azeotropic dehydration tower.

  In the present invention, it is preferable that the polymerization inhibitor is supplied from any place other than the raw material supply stage and from the reflux liquid supply stage in any distillation column. More preferably, the polymerization inhibitor is administered depending on the composition in the tower from any of the raw material supply stage to the reflux liquid supply stage (excluding the reflux liquid supply stage). As the method, together with the reaction product solution containing acrylic acid, it can be supplied by the atomization means with one or more spray nozzles previously disposed in the distillation column. This is because the polymerization inhibitor-containing solution can be sprayed over a wide range inside the distillation tower by spraying, and polymerization can be effectively prevented. Even when charged from the raw material supply stage and the reflux liquid supply stage, the polymerization inhibitor can be charged by a dedicated spray nozzle different from the raw material and the reflux liquid. It is also possible to mix and mix the mixed solution with a spray nozzle. In addition, since there is little change in the acrylic acid concentration in the high boiling point substance separation tower, it can be supplied from other than the raw material supply stage and the reflux liquid supply stage, and may be supplied from the raw material supply stage and / or the reflux liquid supply stage. . At this time, it is preferable to use a part of the column top distillate as acrylic acid. The high-boiling-point separation column is a device for obtaining acrylic acid, because the product quality is stabilized by using a distillate that is substantially the same quality as the product (raw material as ester and high-purity acrylic acid). is there.

  In the present invention, a distillate gas containing acrylic acid is obtained from the top of the high-boiling-point material separation tower and condensed, and at least a part of the resulting acrylic acid-containing condensate is supplied to the azeotropic dehydration tower. Good. In general, the condensate is a product acrylic acid used as an ester / high-purity acrylic acid raw material, and the column bottom liquid contains a polymerization inhibitor, an acrylic acid oligomer, and other high-boiling substances. In the present invention, the liquid at the bottom of the column is referred to as a high-boiling substance-containing liquid, and a step of recovering acrylic acid by thermally decomposing an acrylic acid oligomer contained therein is performed.

  The thermal decomposition of the acrylic acid oligomer is performed in a thermal decomposition tank. There is no particular limitation on the type of pyrolysis tank. However, since the viscosity is high and in some cases solids are deposited and the liquid properties are poor, the liquid circulation and / or stirrer is installed so that the composition in the tank can be made uniform with an inclination toward the liquid outlet. Is preferred.

  Moreover, the thermal decomposition temperature in a thermal decomposition tank is 120-220 degreeC normally, and the range of 120 degreeC-160 degreeC is especially suitable. Although the residence time (the amount of liquid in the thermal decomposition tank / the amount of waste oil) varies depending on the thermal decomposition temperature, it cannot be specified unconditionally, but usually it requires about 20 to 50 hours. For this reason, a heating means is required for the thermal decomposition tank, but if a jacket and / or an internal (or external) heat exchanger is installed in the tank and the decomposition temperature is maintained using a heat medium such as steam or oil. Good.

  In the present invention, a polymerization inhibitor may be added to the high-boiling point substance-containing liquid during thermal decomposition in a thin film evaporator or a thermal decomposition tank. In some cases, polymerization can be efficiently prevented and thermal decomposition is promoted. Among the above-described polymerization inhibitors having an action of promoting thermal decomposition, among these, 4,4 ′, 4 ″ -tris- (2,2,6,6-tetramethylpiperidinooxyl) phosphite and 2 , 2,6,6-Tetramethylpiperidinooxyls:

(In the formula (1), R ₁ represents CH ₂ , CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, CHOCH ₂ CH ₂ OH, CHCOOH, or C═O, and R ₂ represents hydrogen. One or more of the compounds represented by Atom or CH ₂ OH), N-hydroxy-2,2,6,6-tetramethylpiperidine compounds such as 1,4-dihydroxy-2,2,6, 2,2,6,6-tetramethylpiperidine compounds such as 6-tetramethylpiperidine, 1-hydroxy-2,2,6,6-tetramethylpiperidine, such as 2,2,6,6-tetramethylpiperidine, One or more kinds such as 4-hydroxy-2,2,6,6-tetramethylpiperidine can be used in combination.

  The acrylic acid recovered by thermal decomposition of the oligomer is preferably supplied to the separation step. As described above, it is possible to purify impurities such as water contained in the subsequent steps and to effectively use the polymerization inhibitor. That is, it is suitable in terms of both improvement of product quality by preventing moisture in the product and prevention of precipitation of the polymerization inhibitor.

  The acrylic acid distilled from the top of the high boiling point substance separation tower can be produced by supplying it to the acrylic ester production process.

  The distillation operation can be used not only when lactic acid is used as a raw material but also when a lactic acid ester is used.

  The amount of 2,3-pentanedione contained in the phase containing the crude acrylic acid separated in the 2,3-pentanedione removal step (B-1) is the mass ratio of 2,3-pentanedione to acrylic acid. Is preferably 0.01 or less, more preferably 0.005 or less, and still more preferably 0.001 or less.

<Method of producing acrylic acid and / or acrylic ester using lactic acid ester as a raw material>
Regarding a method for producing acrylic acid and / or acrylic acid ester using lactic acid ester as a raw material according to another embodiment of the present invention, lactic acid ester is subjected to a dehydration reaction, and includes acrylic acid ester, water, and 2,3-pentanedione. Step (A-2) for obtaining a dehydration reaction product, Step (C-2) for obtaining acrylic acid by subjecting the acrylic ester contained in the dehydration reaction product to a hydrolysis reaction, Acrylic ester, acrylic acid and 2 , 3-pentanedione is separated from the phase (B-2), and the phase containing an acrylic ester is purified to obtain a high-purity acrylic acid (D-2).

  FIG. 2 is a production flow chart according to a method for co-producing acrylic acid and acrylic acid ester from lactic acid ester. In FIG. 2, the lactic acid ester is heated and vaporized in the dehydration step A-2, and after the gas phase dehydration reaction is generated through a fixed bed reactor filled with a solid catalyst to produce an acrylate ester, the reaction gas is cooled. Liquefaction. At this time, a part of the acrylic ester is sequentially hydrolyzed to simultaneously produce acrylic acid. In the hydrolysis step C-2, water is subsequently added to hydrolyze the acrylic ester, whereby a part of the acrylic ester is hydrolyzed to acrylic acid and alcohol, and these are converted into water and 2,3-pentanedione. A containing phase is obtained.

  In the separation step (B-2), acrylic acid ester and alcohol are distilled from the top of the column by distillation, and acrylic acid, water, and 2,3-pentanedione are recovered from the bottom of the column. In the purification step D-2, the phase containing an acrylate ester and alcohol obtained from the top of the column is separated into a crude acrylate ester and a phase containing alcohol and water by an extraction operation or the like. Further purification by the method results in a purified acrylic acid ester. From the phase containing alcohol and water, the alcohol can be recovered by distillation or the like and reused in the synthesis of the lactic acid ester. Acrylic acid, water, and 2,3-pentanedione recovered from the bottom of the column are obtained by applying the separation step B-1 in the method for producing an acrylate ester from lactic acid to obtain crude acrylic acid and 2,3-pentanedione. The crude acrylic acid is purified by a method such as distillation or crystallization to become purified acrylic acid.

  FIG. 3 is a production flowchart according to a method for producing only acrylic acid from a lactic acid ester. FIG. 3 is the same as the method of co-producing acrylic acid and acrylic ester from the lactic acid ester shown in FIG. 2 until the purification step (D-2), but the resulting crude acrylic ester is hydrolyzed. It is different in that it is recycled to (C-2). In the case of producing only acrylic acid, the acrylic ester is recycled for use in the hydrolysis step, so the conditions of the separation step such as distillation are acrylic acid, so that 2,3-pentanedione is not included on the acrylic ester side. It is necessary to adjust so that it is separated to the water side. By doing so, 2,3-pentanedione accumulates during the steps of the purification step (D), the recycling step (E), the hydrolysis step (C-2), and the separation step (B-2). Thus, 2,3-pentanedione can be removed from the system together with the waste water in the purification step of the crude acrylic acid.

[Dehydration step (A-2)]
The dehydration step (A-2) is a method for producing acrylic acid and / or an acrylic ester using a lactic acid ester as a raw material, subjecting the lactic acid ester to a dehydration reaction, and dehydration containing acrylic acid, water, and 2,3-pentanedione. This is a step of obtaining a reaction product.

(Lactic acid ester)
Although it does not specifically limit as a lactic acid ester used for reaction, Carbon number of the ester group part is 2-20, Preferably it is 2-10, More preferably, it is 2-5.

  The lactic acid ester used for the dehydration reaction may be a stock solution or an aqueous solution. When an aqueous solution is used, the concentration of the lactic acid ester aqueous solution is preferably 30% by mass or more, more preferably 50% by weight or more, and further preferably 70% by mass or more. It is.

  The reaction apparatus, solid catalyst, reaction conditions, etc. used in the dehydration step are the same as in the case of using lactic acid as a raw material.

[Hydrolysis step (C-2)]
The hydrolysis step (C-2) is a step of hydrolyzing the acrylic ester produced in the dehydration step A-2 into acrylic acid and alcohol. Specifically, the reaction product generated in the dehydration step (A-2) is aggregated through a cooler, water is added, and then a hydrolysis reaction is performed with heating as necessary in the presence of a catalyst.

  The type of the hydrolysis reaction is not particularly limited, and examples thereof include a stirring reactor, a fixed bed type, a fluidized bed type, and a spouted bed type, and a fixed bed type is preferable.

  The amount of water added in the hydrolysis reaction is not generally determined because it depends on the amount of acrylic ester after the dehydration step (A-2), but it is more than twice the molar ratio of the lactic acid ester used. Furthermore, if it is more than 5 times, the equilibrium is sufficiently biased toward the acrylic acid side, which is preferable. In the case of 50 times or less, more specifically in the case of 10 times or less, it is preferable from the viewpoint of suppressing energy input during distillation.

  In the hydrolysis reaction, if no catalyst is used, the reaction time becomes long, and polymerization and side reactions may proceed. Therefore, it is preferable to use a catalyst. As the catalyst, a metal compound, an acid catalyst, a base catalyst, a heterogeneous catalyst or the like is used, and an acid catalyst is preferable.

  Examples of the acid catalyst include strongly acidic ion exchange resins, metal oxides such as silica, alumina, silica alumina, γ-alumina, zirconia, and titania; various zeolites such as HY zeolite and mordenite. Of these, various strongly acidic ion exchange resins such as γ-alumina, zirconia, titania, and Nafion, and various zeolites are more preferable. One type of dehydration catalyst may be used, or two or more types may be used in combination.

  The reaction temperature is preferably 40 ° C. or higher and 100 ° C. or lower, more preferably 50 ° C. or higher and 80 ° C. or lower.

[Acrylic acid / acrylic acid ester separation step (B-2)]
In the separation step (B-2), the dehydration reaction product containing acrylic acid, acrylic ester, water, and 2,3-pentanedione obtained in the dehydration step (A-2) is converted into the acrylic ester. It is the process of isolate | separating into the phase containing and the phase containing acrylic acid. The separation operation is not particularly limited, and examples thereof include distillation, membrane separation, and extraction, and distillation is preferable.

(distillation)
The distillation step in this embodiment is a step of collecting a gaseous dehydration reaction product containing acrylic acid, acrylic ester, water, and 2,3-pentanedione to obtain a dehydration reaction product solution, In this step, the physical solution is separated into a phase containing acrylic acid and a phase containing acrylic ester. 2,3-pentanedione is contained in either the phase containing acrylic acid or the phase containing acrylate ester depending on the separation conditions. When co-producing crude acrylic acid and crude acrylic ester, 2,3-pentanedione may be distilled off together with acrylic ester and alcohol from the top of the column, or recovered together with acrylic acid from the bottom of the column. Good.

  However, when only acrylic acid is produced, 2,3-pentanedione must be recovered from the tower bottom together with acrylic acid. This is because, as shown in FIG. 3, the distillate containing the acrylate ester is returned to the hydrolysis step (C-2), so that 2,3-pentanedione is distilled out together with the acrylate ester. This is because 2,3-pentanedione is accumulated without being discharged. This is the same when the separation step is performed by a method other than distillation.

  When only acrylic acid is produced, the amount of 2,3-pentanedione contained in the phase containing the acrylic ester separated in the acrylic acid / acrylic ester separation step (B-2) is acrylic acid. The mass ratio of 2,3-pentanedione to ester is preferably 0.01 or less, more preferably 0.005 or less, and still more preferably 0.001 or less.

  As described above, 2,3-pentanedione is removed from the acrylic acid ester solution containing 2,3-pentanedione distilled from the top of the column or the acrylic acid solution containing 2,3-pentanedione recovered from the bottom of the column. This operation can be carried out by combining the 2,3-pentanedione removal step after the separation step (B-2). When 2,3-pentanedione is distilled from the top of the column together with the acrylate ester in the step (B-2), the acrylate ester and 2,3-pentanedione are separated before the purification step D. The separation operation may be controlled. If the separation operation is a distillation operation, the distillation conditions such as the number of plates, the reflux ratio, and the distillation rate may be appropriately determined so that the acrylate ester and 2,3-pentanedione are separated. Good. This separation operation can be performed simultaneously with the purification step from the crude acrylate ester to the product acrylate ester in the purification step D. For example, when the separation of 2,3-pentanedione and the purification of acrylic ester are both distillation operations, the separation of 2,3-pentanedione and the purification of acrylic ester can be performed simultaneously by the same distillation operation. When 2,3-pentanedione is recovered from the column bottom together with acrylic acid in the separation step (B-2), only the acrylic ester is removed by the 2,3-pentanedione removal step (B-1). Control may be made so as to recover from the waste.

  The distillation column and distillation operation to be used can be selected and implemented following the 2,3-pentanedione removal step (B-1) when lactic acid is used as a raw material.

[Purification step (D)]
The purification step (D) is a step of removing water or alcohol contained in the acrylic acid or acrylate ester-containing phase that does not contain 2,3-pentanedione obtained in the separation step (B-2), and This is a step of purifying crude acrylic acid or crude acrylic ester. For the purification operation, a known purification method such as distillation, crystallization, solvent extraction, chromatography or the like may be employed. Among them, from the viewpoint of both product purity and production efficiency, distillation is an acrylic resin for purification of crude acrylate. Crystallization is preferred for acid purification.

  In the co-production of acrylic acid and acrylic ester using the acrylic ester of FIG. 2 as one embodiment of the present application, a fraction containing acrylic ester, alcohol, and water obtained in the separation step (B-2). The portion is first washed with water to remove alcohol. Subsequently, distillation is performed to remove water contained in the obtained crude acrylic acid ester.

  In addition, in the production of acrylic acid using the acrylic ester of FIG. 3 which is another embodiment of the present application, a distillate containing acrylic ester, alcohol and water obtained in the separation step (B-2). Is washed with water to remove alcohol and then returned to the hydrolysis step (C-2).

  The distillation of the acrylic acid ester in the purification step (D) can be performed following the method described in the above-mentioned 2,3-pentanedione removal step (B-1).

  Crystallization of acrylic acid in the purification step (D) can be carried out following a known method as described in WO / 2011/001887.

  What is necessary is just to perform the water washing process for alcohol removal in a refinement | purification process (D) according to a conventional method. Specifically, a method of adding water or an inorganic aqueous solution to the reaction solution obtained by the esterification reaction or the neutralization treatment solution, stirring and mixing, and the like can be mentioned. In the washing step, water is usually used. On the other hand, when the separation from the organic layer is improved or a high-purity product is required, an inorganic aqueous solution is preferably used. Specifically, an aqueous ammonium salt solution such as an aqueous ammonium sulfate solution and an aqueous ammonium chloride solution, Examples include aqueous sodium salt solutions such as sodium chloride, and acidic water such as aqueous hydrochloric acid.

  Moreover, it can heat as needed. An example of the heating temperature is 30 to 80 ° C., and an example of the heating time is 5 minutes to 5 hours. In the case of heating, it is preferable to use the polymerization inhibitor described in the 2,3-pentanedione removal step (B-1) for the purpose of preventing polymerization.

[Recycling process (E)]
In the recycling step (E), when only acrylic acid is produced from the lactic acid ester shown in FIG. 3 which is one embodiment of the present invention, the crude acrylic acid ester obtained in the purification step (D) is hydrolyzed ( This is the step of returning to C-2). Since hydrolysis of the acrylic ester in the hydrolysis step (C-1) is an equilibrium reaction, a certain amount of acrylic ester is produced in the separation step. The raw material can be used effectively by returning to the acrylate ester hydrolysis step repeatedly.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited at all by the following Example. In the following description, “part” or “%” may be used, but “part by mass” or “% by mass” is indicated unless otherwise specified.

(Catalyst preparation example)
A calcium phosphate-calcium pyrophosphate catalyst was prepared with reference to Applied Catalysis A: General 396 (2011) 194-200. The catalyst was a powdered calcium phosphate-calcium pyrophosphate catalyst that was compressed and molded with a hydraulic press and then crushed, and sieved to a particle size of about 1 mm.

(Reaction example 1)
As a raw material, a fixed bed reactor in which 1 kg / h of a 50 mass% lactic acid aqueous solution was kept at 360 ° C. in a night bath with nitrogen of 2.3 L / h as a carrier gas (reaction tube inner diameter 2 cm, catalyst layer length 1.5 m, Gas phase dehydration reaction was performed by supplying 350 ml of the catalyst produced in step 1) at a pressure of 101 kPa. The gas exiting the reactor was condensed through a condenser and recovered as a liquid. The composition of the obtained condensate is 30.4% by mass of acrylic acid, 62.5% by mass of water, 5.9% by mass of acetaldehyde, 0.6% by mass of propionic acid, 0.2% by mass of hydroxyacetone, 2, 3 -It was 0.2 mass% of pentanedione.

(Example 1) (Lactic acid raw material: Example 1 in which 2,3-pentanedione is sufficiently removed)
The condensate obtained in Reaction Example 1 is continuously fed at 0.956 kg / h to a distillation column having 40 theoretical plates, and a distillate can be obtained at a reflux ratio of 5 and 0.65 kg / h from the top of the column. As a result, crude acrylic acid was obtained at 0.30 kg / h from the bottom of the column. The composition of this crude acrylic acid is 89.7% by mass of acrylic acid, 9.0% by mass of water, 0.6% by mass of propionic acid, 0.7% by mass of hydroxyacetone, and 2,3-pentanedione is contained. There wasn't. When this crude acrylic acid was used as a mother liquor for purification by crystallization, 99.9% by mass of acrylic acid was obtained.

(Example 2) (Lactic acid raw material: Example 2 in which 2,3-pentanedione is sufficiently removed)
The condensate obtained in Reaction Example 1 was continuously supplied at 0.956 kg / h and toluene at 2.69 kg / h to a distillation column having 30 theoretical plates, the reflux ratio was 1, and 3.05 kg / h from the top of the column. As a result of the operation so as to obtain a distillate, a liquid containing water and toluene as main components was distilled from the top of the column. The liquid extracted from the bottom of the column was continuously supplied to a distillation column having 30 theoretical plates, and the distillate was operated at a reflux ratio of 1.5 and 0.31 kg / h from the top of the column. As a result, crude acrylic acid was obtained from the tower bottom at 0.29 kg / h. The composition of this crude acrylic acid was 97.1% by mass of acrylic acid, 1.7% by mass of propionic acid, 0.5% by mass of hydroxyacetone, and no 2,3-pentanedione was contained. When this crude acrylic acid was used as a mother liquor for purification by crystallization, 99.9% by mass of acrylic acid was obtained.

(Reaction example 2)
As a raw material, fixed bed reactor (reactor tube inner diameter: 2 cm, catalyst layer length: 1.5 m, manufactured above) with methyl lactate (0.5 kg / h) kept at 360 ° C. with nitrogen gas (2 L / h) as a carrier gas. Gas phase dehydration reaction was performed by supplying the catalyst at a pressure of 101 kPa. The gas coming out of the reactor is condensed through a cooler, water is added at 0.5 kg / h, and then supplied to a column packed with a strongly acidic ion exchange resin (Nafion) and kept at 70 ° C. for hydrolysis reaction. went. The composition of the obtained reaction solution was acrylic acid 16.6% by mass, methyl acrylate 19.2% by mass, water 51.2% by mass, methanol 7.4% by mass, acetaldehyde 4.3% by mass, propionic acid 1 0.1% by mass and 0.2% by mass of 2,3-pentanedione.

(Example 3) (Example of co-production of acrylic acid and acrylic ester from lactic acid ester raw material: an example in which 2,3-pentanedione is sufficiently removed)
The reaction solution obtained in Reaction Example 2 was continuously fed at 1.69 kg / h to a distillation column having a theoretical plate number of 20 so that a distillate could be obtained at a reflux ratio of 2 and 0.55 kg / h from the top of the column. As a result, the distillate (1) mainly composed of methanol and methyl acrylate was distilled from the top of the tower, and the bottom liquid (2) mainly composed of water and acrylic acid was removed from the bottom of the tower. It was issued. The bottoms (2) was continuously supplied to a distillation column having a theoretical plate number of 40, and was operated so as to obtain a distillate at a reflux ratio of 10 and 0.84 kg / h from the top of the column. Crude acrylic acid was obtained at 0.30 kg / h. The composition of this crude acrylic acid was 85.5% by mass of acrylic acid, 13.0% by mass of water and 1.5% by mass of propionic acid, and no 2,3-pentanedione was contained. When purification by crystallization was performed using this crude acrylic acid as a mother liquor, 99.9% by mass of high-purity acrylic acid was obtained, and 2,3-pentanedione was not contained. On the other hand, distillate (1) was obtained by extracting and removing methanol by washing with water to obtain crude methyl acrylate. The composition of the obtained crude methyl acrylate was 93.7% by mass of methyl acrylate and 0.3% by mass of water. %, Methanol 0.3% by mass, and acetaldehyde 5.8% by mass. The crude acrylic acid was continuously supplied to a distillation column having a theoretical plate number of 20 at 0.35 kg / h, and the distillate was obtained at a reflux ratio of 1.5 and 0.03 kg / h from the top of the column. As a result, methyl acrylate having a purity of 99.7% by mass was obtained from the bottom of the column at 0.32 kg / h, and 2,3-pentanedione was not contained.

(Example 4) (Example in which only acrylic acid is produced from a lactic acid ester raw material: 2,3-pentanedione is sufficiently removed)
The condensate obtained in Reaction Example 2 was continuously fed at 1.69 kg / h to a distillation column having 20 theoretical plates, and a distillate was obtained at a reflux ratio of 2 and 0.55 kg / h from the top of the column. As a result, the distillate (1) mainly composed of methanol and methyl acrylate was distilled from the top of the tower, and the bottom liquid (2) mainly composed of water and acrylic acid was removed from the bottom of the tower. It was issued. The bottoms (2) was continuously supplied to a distillation column having a theoretical plate number of 40, and was operated so as to obtain a distillate at a reflux ratio of 10 and 0.84 kg / h from the top of the column. Crude acrylic acid was obtained at 0.30 kg / h. The composition of this crude acrylic acid was 85.5% by mass of acrylic acid, 13.0% by mass of water and 1.5% by mass of propionic acid, and no 2,3-pentanedione was contained. When purification by crystallization was performed using this crude acrylic acid as a mother liquor, 99.9% by mass of high-purity acrylic acid was obtained, and 2,3-pentanedione was not contained. On the other hand, distillate (1) was obtained by extracting and removing methanol by washing with water to obtain crude methyl acrylate. The composition of the obtained crude methyl acrylate was 93.7% by mass of methyl acrylate and 0.3% by mass of water. %, Methanol 0.3% by mass, and acetaldehyde 5.8% by mass. This crude acrylic acid does not contain 2,3-pentanedione and can be recycled as a raw material for the hydrolysis reaction.

(Comparative Example 1) (Lactic acid raw material: an example with a large residual amount of 2,3-pentanedione)
The condensate obtained in Reaction Example 1 is continuously supplied at 0.93 kg / h to a distillation column having 30 theoretical plates, and a distillate can be obtained at a reflux ratio of 5 and 0.36 kg / h from the top of the column. As a result, crude acrylic acid was obtained from the tower bottom at 0.57 kg / h. The composition of this crude acrylic acid was 78.1% by mass of acrylic acid, 11.2% by mass of water, 1.3% by mass of propionic acid, 0.6% by mass of hydroxyacetone, 0.2% by mass of 2,3-pentanedione. Met.

Claims (7)

  In a method for producing acrylic acid and / or acrylic ester from lactic acid and / or lactic ester, acrylic acid and / or comprising removing 2,3-pentanedione from a solution containing acrylic acid and / or acrylic ester Or the manufacturing method of acrylic ester.   The method for producing acrylic acid according to claim 1, wherein the method comprises producing acrylic acid from lactic acid, the method comprising removing 2,3-pentanedione from a solution containing acrylic acid. Subjecting lactic acid to a dehydration reaction to obtain a dehydration reaction product containing acrylic acid, water, and 2,3-pentanedione (A-1);
Removing 2,3-pentanedione from the dehydration reaction product (B-1);
The manufacturing method of acrylic acid of Claim 2 containing this.   The method for producing acrylic acid and / or acrylic ester from lactic acid ester, comprising removing 2,3-pendandione from a solution containing acrylic acid and / or acrylic ester. A method for producing acrylic acid and / or acrylic ester. A step (A-2) of subjecting a lactic acid ester to a dehydration reaction to obtain a dehydration reaction product containing an acrylic ester, water, and 2,3-pentanedione;
A step of subjecting the acrylic ester contained in the dehydration reaction product to a hydrolysis reaction to obtain acrylic acid (C-2);
A step (B-2) for separating a phase containing an acrylic ester and a phase containing acrylic acid;
Removing 2,3-pentanedione from the solution containing acrylic acid or acrylic ester (B-1);
The manufacturing method of acrylic acid and / or acrylic ester of Claim 4 containing these.   Step (D) for purifying the phase containing crude acrylic acid or crude acrylic ester not containing 2,3-pentanedione obtained in the step (B-2) to obtain crude acrylic acid or crude acrylic ester The manufacturing method of acrylic acid and acrylic ester of Claim 5 which has these.   The manufacturing method of acrylic acid of Claim 6 which has the process (E) which returns the crude acrylic acid ester obtained at the said process (D) to a hydrolysis process (C-2).

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