JP2008280349A - Method for producing acrylic acid, apparatus for producing acrylic acid, and composition for producing acrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for producing acrylic acid at a high yield from an acrolein-containing composition, and to provide the acrolein-containing composition. <P>SOLUTION: The method for producing acrylic acid comprises a refining step of removing phenol and/or 1-hydroxyacetone from an acrolein-containing composition and an oxidation step of producing acrylic acid by oxidizing acrolein in the acrolein-containing composition after the refining step. The apparatus for the method comprises a refiner to be used in the refining step and an oxidation reactor for producing the acrylic acid by oxidizing the acrolein. The acrolein-containing composition has ≤0.020 of (phenol mass)/(acrolein mass) and ≤0.020 of (1-hydroxyacetone mass)/(acrolein mass). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing acrylic acid, an apparatus for producing acrylic acid, and a composition for producing acrylic acid.

  Acrolein is used as a raw material for acrolein derivatives such as 1,3-propanediol, methionine, acrylic acid, and 3-methylthiopropionaldehyde. It is known that acrolein can be produced by dehydrating glycerin.

  For example, Patent Document 1 discloses that when glycerin is dehydrated, an acrolein-containing composition containing allyl alcohol, acetaldehyde, propionaldehyde, and 1-hydroxyacetone as byproducts can be produced. A method for producing 1,3-propanediol by using the composition having an increased acrolein concentration as a raw material and reducing acrolein in the raw material is disclosed. Patent Document 2 discloses a method for producing acrylic acid by gas phase oxidation of acrolein in a composition produced by vapor phase dehydration reaction of glycerin.

As described above, various compounds are produced from acrolein as an acrolein derivative. However, it is desired to produce any derivative with good yield. Even in the case of producing acrylic acid, it is no exception that a production method with good yield is desired.
JP-A-6-217724 JP 2005-213225 A

  In view of the above circumstances, an object of the present invention is to provide a technique capable of producing acrylic acid with high yield from an acrolein-containing composition.

  This inventor repeated examination about whether the compound in an acrolein containing composition affects the yield of acrylic acid. As a result, it was found that phenol and 1-hydroxyacetone cause a decrease in the yield of acrylic acid, and the present invention has been completed.

  That is, the present invention comprises a purification step for removing phenol and / or 1-hydroxyacetone from an acrolein-containing composition, and an oxidation step for producing acrylic acid by oxidizing acrolein in the acrolein-containing composition after the purification step. It is a manufacturing method of acrylic acid which has. Here, the “acrolein-containing composition” in the present manufacturing method invention includes a composition containing acrolein and phenol; a composition containing acrolein and 1-hydroxyacetone; or acrolein, phenol and 1-hydroxyacetone. A composition; a liquid or gaseous composition.

  The method for producing acrylic acid may have a dehydration step of dehydrating glycerin to produce acrolein before the purification step. This dehydration step is, for example, a step of dehydrating glycerin in the gas phase.

  The present invention also provides a purifier for removing phenol and / or 1-hydroxyacetone from an acrolein-containing composition, and an oxidation for producing acrylic acid by oxidizing acrolein in the acrolein-containing composition purified by the purifier. An apparatus for producing acrylic acid having a reactor.

  Moreover, this invention is a manufacturing method of an acrylic acid derivative which has the process of manufacturing acrylic acid using the said manufacturing method of acrylic acid. Here, the “acrylic acid derivative” is a compound using acrylic acid as a raw material, and examples thereof include acrylic acid esters, polyacrylic acid and salts thereof.

  The present invention also relates to a composition for producing acrylic acid containing acrolein, wherein the ratio (P / A) of the mass (A) of acrolein to the mass (P) of phenol is 0.020 or less, and the mass of acrolein ( It is a composition for acrylic acid manufacture whose ratio (H / A) of A) and the mass (H) of 1-hydroxyacetone is 0.020 or less.

  According to the production method and apparatus of the present invention, phenol and / or 1-hydroxyacetone is removed from the acrolein-containing composition, so that acrylic acid can be produced in a high yield.

  Furthermore, according to the composition of the present invention, since the amount of phenol and / or 1-hydroxyacetone relative to acrolein is not more than a predetermined amount, acrylic acid can be produced with good yield.

  The present invention will be described below based on embodiments. The method for producing acrylic acid according to this embodiment is a method having a purification step of removing phenol and / or 1-hydroxyacetone from an acrolein-containing composition and an oxidation step of oxidizing acrylic acid after the purification step. Hereinafter, the method of this embodiment is demonstrated for every process.

First, the purification process will be described.
The acrolein-containing composition used in the purification process contains phenol and / or 1-hydroxyacetone. The acrolein-containing composition is produced by a glycerin gas phase dehydration reaction using glycerin gas or a glycerin liquid phase dehydration reaction using liquid glycerin. In these dehydration reactions, a catalyst is used.

As a catalyst that can be used in the dehydration reaction, natural or synthetic clay compounds such as zeolite, kaolinite, bentonite, montmorillonite such as H-ZSM5 as representative examples; sulfuric acid, phosphoric acid or phosphate (alkali metal salt of phosphoric acid, phosphorus Catalysts in which manganese acid, zirconium phosphate, etc.) are supported on alumina; Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , V ₂ O ₅
, SiO ₂ —Al ₂ O ₃ , SiO ₂ —TiO ₂ , TiO ₂ —WO ₃ and other inorganic oxides or inorganic composite oxides; MgSO ₄ , Al ₂ (SO ₄ ) ₃ , K ₂ SO ₄ , AlPO ₄ , Solid acidic substances such as sulfates, carbonates, nitrates, and phosphates of metals such as Zr ₃ (SO ₄ ) ₂ are exemplified. In addition, zirconium oxide supporting phosphoric acid, sulfuric acid, or tungsten oxide, or a solid acid disclosed in International Publications WO2006 / 087083 and WO2006 / 087084 is used as a catalyst for the dehydration reaction of glycerin. Can do. The shape of the catalyst used for these dehydration reactions is not limited, and may be spherical, columnar, ring-shaped, or bowl-shaped.

Taking the vapor phase dehydration reaction of glycerin as an example, the production conditions of the acrolein-containing composition will be described in more detail. The gas phase dehydration reaction is performed by bringing a reaction gas containing glycerin into contact with a catalyst in a reactor arbitrarily selected from a fixed bed reactor, a moving bed reactor, and the like.

  The reaction gas may be a gas composed only of glycerin or may contain a gas for adjusting the glycerin concentration in the reaction gas. Examples of the gas for adjusting the concentration include water vapor, nitrogen, and air. The glycerin concentration in the reaction gas may be 0.1 to 100 mol%, preferably 1 mol% or more, and 10 mol% or more in order to produce acrolein economically and highly efficiently.

In the gas phase dehydration reaction, the reaction gas is preferably circulated in the reactor from the viewpoint of production efficiency. The flow rate of the reaction gas at this time is 100 to 10,000 hr in terms of the reaction gas flow rate (GHSV) per unit catalyst volume. ^-1 is good. Preferably, it is 5000 hr ⁻¹ or less, and 3000 hr ⁻¹ or less in order to produce acrolein economically and with high efficiency. The gas phase dehydration reaction temperature is not particularly limited, but is preferably 200 to 500 ° C, preferably 250 to 450 ° C, more preferably 300 to 400 ° C, and the pressure of the reaction gas. The pressure may be in a range where glycerin gas does not condense, and is usually 0.001-1 MPa, preferably 0.01-0.5 MPa.

  According to the vapor phase dehydration reaction of glycerin, a gaseous acrolein-containing composition is produced. In order to collect the gaseous composition, a method in which the gaseous acrolein-containing composition is cooled and liquefied, or a method in which the gaseous composition is absorbed in a solvent such as water having an acrolein dissolving ability may be used.

  As described above, the present inventors have found that the acrolein-containing composition from which phenol or 1-hydroxyacetone has been removed is suitable as a composition for producing acrylic acid. The background is as follows.

  The present inventor prepared a composition in which phenol, 1-hydroxyacetone, or allyl alcohol, which is a by-product in the production of acrolein, was added to acrolein, and conducted an acrylic acid production experiment using this composition as a raw material.

The above experiment was performed as follows. A reaction gas was circulated (GHSV: 2000 hr ⁻¹ ) through a stainless steel reaction tube filled with 20 cc of an acrylic acid production catalyst (acrylic acid production catalyst in Example 1 described later) to produce acrylic acid at a reaction temperature of 230 ° C. It was. And the gas which flowed out from the reaction tube between the start of distribution for 60 to 80 minutes was collected, and this component was analyzed by gas chromatography. The reaction gas in this experiment includes 33.36 parts by volume of water vapor (Experiment No. 1); 33.18 parts by volume of water vapor and 0.18 parts by volume of phenol (Experiment No. 2); And 0.36 part by volume of 1-hydroxyacetone (Experiment No. 3); or 33.00 part by volume of water vapor and 0.36 part by volume of allyl alcohol (Experiment No. 4); and 54.4 parts by volume of nitrogen, A gas having 10.44 parts of oxygen and 1.8 parts by volume of acrolein as components was used.

The results of this experiment are as shown in Table 1 below.

  As shown in Table 1, when an acrolein-containing composition containing phenol (Experiment No. 2) or 1-hydroxyacetone (Experiment No. 3) is used as a raw material, an acrolein composition to which these compounds are not added is used. It is worse than the conversion rate of acrolein and the yield of acrylic acid. From this, it was decided to remove phenol or 1-hydroxyacetone from the acrolein-containing composition.

  In addition, from the said experimental result, when 1-hydroxyacetone is removed, it turns out that the byproduct of an acetic acid can be suppressed.

As described above, when phenol or 1-hydroxyacetone is contained in the acrolein-containing composition, the yield of acrylic acid is deteriorated. This is presumed to be the following reason. Phenol and acrolein are presumed to form a polymerized compound at the acid or base point of the acrylic acid production catalyst, as well as polymerize and polymerize in the presence of acid or base. And as a result of the said compound having arisen also at the acid point etc. of the catalyst for acrylic acid manufacture, the active site of this catalyst is coat | covered, and it is estimated that the yield of acrylic acid deteriorates. Further, when 1-hydroxyacetone is contained, a large amount of acetic acid is produced, and therefore it is presumed that 1-hydroxyacetone subjected to the oxidizing action of the acrylic acid production catalyst is converted to acetic acid. Such conversion is presumed to deteriorate the yield of acrylic acid by reducing the catalytic activity point for converting acrolein to acrylic acid.

  Since phenol and 1-hydroxyacetone are compounds that reduce the yield of acrylic acid, the removal amount of both compounds is preferably as large as possible. The amount of phenol in the acrolein-containing composition after removal is expressed by the ratio (P / A) of the mass (A) of acrolein to the mass (P) of phenol, and P / A is 0.020 or less. Preferably, it is 0.010 or less, more preferably 0.005 or less. Further, the amount of 1-hydroxyacetone in the acrolein-containing composition after removal can be expressed as H / A by the ratio (H / A) of the mass (A) of acrolein and the mass (H) of 1-hydroxyacetone. Is preferably 0.020 or less, more preferably 0.010 or less, and still more preferably 0.005 or less.

As described above, the larger the removal amount of phenol and 1-hydroxyacetone, the better. However, as this removal amount is increased, the problem of increasing the loss of acrolein and the problem of complication of the purification process are likely to occur. These problems are likely to occur when phenol is removed by a purification method involving heating such as a distillation operation. In consideration of this, P / A is preferably 1 × 10 ⁻⁹ or more, preferably 1 × 10 ⁻⁷ or more, more preferably 1 × 10 ⁻⁵ or more. Further, when also the above problems in the removal of 1-hydroxyacetone may the H / A is 1 × 10 ^-9 or higher, preferably 1 × 10 ^-7 or more, more preferably 1 × 10 ^{- 5} or more.

  And a refinement | purification process will be performed in order to make H / A and P / A of an acrolein containing composition into the said range. In this purification step, a purifier appropriately selected from known purifiers is used. In the purification step, before the purification of the acrolein-containing composition using a purifier, separation of water and the like in the acrolein-containing composition by solvent extraction is performed as necessary.

Examples of the purifier that can be used in the purification step of the present embodiment include a distillation column for fractionating low-boiling acrolein in a liquid acrolein-containing composition, and a high condensation temperature phenol in a gaseous acrolein-containing composition. Examples thereof include a condensing tower for condensing and separating 1-hydroxyacetone, and a purifier equipped with a transpiration tower for injecting gas into a stored liquid acrolein-containing composition to vaporize low-boiling acrolein. The purifier exemplified above utilizes the fact that there is a difference in boiling point between acrolein (boiling point: 53 ° C.), phenol (boiling point: 182 ° C.), and 1-hydroxyacetone (boiling point: 146 ° C.), and phenol and / or 1-hydroxyacetone can be easily removed.

  FIG. 1 is a schematic configuration diagram for explaining an example of a purifier according to an embodiment of the present invention. The purifier including the stripping tower exemplified above will be further described with reference to FIG. The illustrated purifier includes a collection tower 1 for condensing a gaseous acrolein-containing composition by cooling and a stripping tower 2 for vaporizing acrolein in the liquid acrolein-containing composition. Among these, the collection tower 1 is supplied with a gaseous acrolein-containing composition ("composition gas" in FIG. 1) from the bottom of the tower, and is not condensed and liquefied by cooling the collection tower 1 from the top of the tower. Release exhaust gas. On the other hand, in the stripping tower 2, a stripping gas for vaporizing the liquid acrolein-containing composition is supplied from the bottom of the tower, and gaseous acrolein-containing composition gas is released from the top of the tower. And the collection tower 1 and the stripping tower 2 are connected by piping as follows. The tower bottom of the collection tower 1 and the tower top of the stripping tower 2 are connected by a delivery pipe 3, and the tower bottom of the radiation tower 2 and the tower top of the collection tower 1 are connected by a return pipe 4.

The purification process of the acrolein-containing composition in the purifier having the configuration shown in FIG. 1 will be described. The liquid acrolein-containing composition cooled and liquefied in the collection tower 1 is supplied to the stripping tower 2 through the delivery pipe 3. A predetermined amount of the liquid acrolein-containing composition is stored in the stripping tower 2, and the liquid acrolein-containing composition that exceeds the predetermined amount due to excessive supply is returned to the collection tower 1 through the return pipe 4. On the other hand, since the liquid acrolein-containing composition stored in the stripping tower 2 is supplied with a stripping gas, acrolein having a lower boiling point than phenol and 1-hydroxyacetone vaporizes preferentially. The gas containing vaporized acrolein is released from the upper part of the stripping tower 2 as a composition gas. The released composition gas may be directly introduced into an oxidation reactor described later.

  As described above, the stripping gas is supplied to the stripping tower 2. The diffusion gas may be at a temperature that can vaporize acrolein. In addition to air, nitrogen, and water vapor, the gas discharged from the acrylic acid absorption tower, which is economically preferable, can be used as the diffusion gas. Moreover, the exhaust gas from the collection tower 1 can also be used as economically preferable emission gas. FIG. 2 is a schematic configuration diagram of a purifier that uses the exhaust gas from the collection tower 1 as a stripping gas. The purifier includes an upper part of the collection tower 1 and a stripping tower 2 in the purifier of FIG. Are connected by a gas introduction pipe 5. If the purifier having the configuration shown in FIG. 2 is used, the exhaust gas from the collection tower 1 can be used as a gas for emission, and in addition, the exhaust that could not be collected by the collection tower 1. All acrolein in the gas can be supplied to the stripping tower 2.

Next, the oxidation process will be described.
In the oxidation step in this embodiment, the catalyst and the gas of the acrolein-containing composition after the purification step coexist in an oxidation reactor arbitrarily selected from a fixed bed reactor, a moving bed reactor, etc., at 200 to 400 ° C. Acrolein is vapor-phase oxidized to produce acrylic acid.

  If the catalyst used in the oxidation reaction is a catalyst used in the case of producing acrylic acid by a contact gas phase oxidation method using acrolein or an acrolein-containing gas and molecular oxygen or a gas containing molecular oxygen, There is no particular limitation. For example, a mixture of metal oxides such as iron oxide, molybdenum oxide, titanium oxide, vanadium oxide, tungsten oxide, antimony oxide, tin oxide, and copper oxide; a composite of metal oxides can be exemplified. Of these exemplified catalysts, a molybdenum-vanadium catalyst in which molybdenum and vanadium are main constituent metals is preferable. The catalyst may be one in which the above mixture and / or composite is supported on a support (for example, zirconia, silica, alumina, and a composite thereof, and silicon carbide).

  The acrolein-containing composition gas used in the oxidation step is preferably added with oxygen from the viewpoint of promoting the oxidation reaction. However, if the oxygen addition amount is exceeded, combustion may occur and there is a risk of explosion. Therefore, the upper limit value is set as appropriate.

  Acrylic acid is produced in the oxidation step, but the acrylic acid generated in the gas phase oxidation step becomes gaseous acrylic acid. In order to recover the acrylic acid, an absorption tower that can cool or absorb the acrylic acid in a solvent such as water is used.

  Since it is known that the produced acrylic acid can be used as a raw material for acrylic acid derivatives such as acrylic acid esters and polyacrylic acid, the production method for acrylic acid is referred to as the production method for acrylic acid derivatives. In the acrylic acid production process.

And when manufacturing polyacrylic acid using the obtained acrylic acid, manufacturing polyacrylic acid which can be used as a water-absorbing resin using aqueous solution polymerization method or reverse phase suspension polymerization method Can do. Here, the aqueous solution polymerization method is a method of polymerizing acrylic acid in an aqueous acrylic acid solution without using a dispersion solvent. US Pat. Nos. 462501, 4873299, 426082, 4973632, 4985518, 5124416 No. 5,250,640, No. 5,264,495, No. 5,145,906 and No. 5,380,808, and European Patent Publication Nos. 081636, 09555086, 0922717, and the like. The reverse phase suspension polymerization method is a polymerization method in which an aqueous solution of acrylic acid as a monomer is suspended in a hydrophobic organic solvent, such as U.S. Pat. Nos. 4,093,764, 4,367,323, 4,446,261, 4,683,274, and No. 5244735.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.

  An acrolein-containing composition was prepared using an acrolein production catalyst and purified from the prepared composition. Then, acrylic acid was produced using the purified composition as a raw material. The details of this manufacturing process are as follows.

(Catalyst for acrolein production)
0.4387 g Cs ₂ CO ₃ and 3.0629 g ammonium dihydrogen phosphate were dissolved in 350 g water, impregnated with 40 g SiO ₂ powder at room temperature, and evaporated to dryness to obtain a catalyst precursor. It was. Next, the catalyst precursor was calcined in the atmosphere at 600 ° C. for 5 hours, and then pulverized and classified to prepare a catalyst for producing acrolein having a particle size of 0.7 to 2.0 mm.

(Preparation of acrolein-containing composition)
A stainless steel reaction tube (inner diameter: 10 mm, length: 500 mm) filled with 15 ml of the acrolein production catalyst was prepared as a fixed bed reactor, and this reactor was immersed in a salt bath at 360 ° C. Thereafter, nitrogen was allowed to flow through the reactor at a flow rate of 61.5 ml / min for 30 minutes, and then a reaction gas (reaction gas composition: glycerin 27 mol%, water 34 mol%, nitrogen 39 mol%) was allowed to flow at a flow rate of 632 hr ^−1. It was. The gas flowing out from the reactor was cooled and liquefied and recovered to prepare an acrolein-containing composition. The liquefaction recovery amount was 94% by mass of the glycerin aqueous solution used.

As a result of quantitative analysis of the prepared acrolein-containing composition by gas chromatography (GC-14B (detector: FID) manufactured by Shimadzu Corporation, packed column ZT-7 manufactured by Shinwa Chemical Co., Ltd.), 31.0% by mass of acrolein was obtained. Analytical values of 1.3% by mass of phenol, 7.5% by mass of 1-hydroxyacetone, 0.1% by mass of glycerin, and 0.1% by mass of allyl alcohol were obtained. As a result of analysis by the Karl Fischer method, an analytical value of 54% by mass of water was obtained.

(Purification of acrolein-containing composition)
The above acrolein-containing composition was purified by distillation using a packed column packed with Dixon packing with a theoretical plate number equivalent to 5 at the top temperature of 46 ° C, the bottom temperature of 100 ° C, the reflux ratio of 3.3, and the normal pressure. did.

  As a result of quantitative analysis of the purified acrolein-containing composition by gas chromatography, an analysis result of 96.7% by mass of acrolein and 0.05% by mass of phenol was obtained, and 1-hydroxyacetone, glycerin and allyl alcohol were detected. There wasn't.

(Manufacture of acrylic acid)
A stainless steel reaction tube (inner diameter 25 mm, length 500 mm) filled with 20 ml of acrylic acid production catalyst was prepared as a fixed bed oxidation reactor, and this reactor was installed in a 230 ° C. night bath. Thereafter, an acrolein-containing gas was circulated in the reactor. Here, as the acrolein-containing gas, a mixture of 1 part by mass of the purified acrolein-containing composition and 5.75 parts by mass of water (flow rate 0.209 g / min), air (flow rate 331.4 ml / min), and nitrogen (flow rate 31). .2 ml / min) was used. After 24 hours from the start of the flow of acrolein gas, the gas flowing out from the reactor was cooled and liquefied and recovered to obtain an acrylic acid-containing composition.

The above acrylic acid production catalyst was prepared as follows. After dissolving 350 g of ammonium paramolybdate, 116 g of ammonium metavanadate, and 44.6 g of ammonium paratungstate in 2500 ml of water with stirring, 1.5 g of vanadium trioxide was added. Separately from this, 87.8 g of copper nitrate was dissolved in 750 ml of heated and stirred water, and then 1.2 g of cuprous oxide and 29 g of antimony trioxide were added. After mixing these two liquids, 1000 ml of spherical α-alumina having a diameter of 3 to 5 mm as a carrier was added and evaporated to dryness with stirring to obtain a catalyst precursor. This catalyst precursor was calcined at 400 ° C. for 6 hours to prepare a catalyst for producing acrylic acid. The supported metal composition of the acrylic acid production catalyst is Mo ₁₂ V _6.1 W ₁ Cu _2.3 Sb _1.2 .

  Moreover, the acrylic acid as a comparison with the said Example was manufactured (comparative example). In this comparative example, (1) using an unpurified acrolein-containing composition that was not distilled, and (2) containing an unpurified acrolein as an acrolein-containing gas to be circulated in the reactor in the production of acrylic acid. A mixture of 1 part by mass of the composition and 1.3 parts by mass of water (flow rate 0.209 g / min), air (flow rate 331.4 ml / min), and nitrogen (flow rate 31.2 ml / min) is used. Except for this, the procedure was the same as in the example.

  Acrolein and acrylic acid in the acrylic acid-containing compositions produced in the above Examples and Comparative Examples were quantified by gas chromatography, and the conversion rate of acrolein, the yield of acrylic acid, and the selectivity of acrylic acid were calculated. Table 2 shows the calculation results. Here, in Table 2, both yield and selectivity are values calculated based on acrolein in the reaction gas.

  As shown in Table 2, the example using the acrolein composition from which phenol and 1-hydroxyacetone were removed was more than the comparative example in all points of acrolein conversion, acrylic acid yield, and acrylic acid selectivity. Excellent. Moreover, in the Example which removed 1-hydroxyacetone, it can confirm that the yield and selectivity of the acetic acid which is a by-product are suppressed low.

A water-absorbent resin was produced using acrylic acid produced by the method according to the above-mentioned example as a raw material. The production method and physical properties of this water-absorbent resin are as follows.

(Manufacture of water absorbent resin)
The acrolein-containing gas prepared in the same manner as in the example was circulated in the fixed bed oxidation reactor (fixed bed: catalyst for producing acrylic acid) in the same manner as in the example. A gas flowing out from the reactor after 24 hours from the start of the flow was absorbed into water to obtain an aqueous acrylic acid solution. This aqueous acrylic acid solution was supplied to a solvent separation tower, and low-boiling impurities such as water and acetic acid were removed from the aqueous acrylic acid solution by azeotropic distillation. Thereafter, the aqueous acrylic acid solution was supplied to the bottom of a high boiling point impurity separation tower having 50 stages of no-weather perforated plates, and distilled at a reflux ratio of 2. In distillation in this high boiling point impurity separation tower, p-methoxyphenol is introduced from the top of the separation tower, and hydrazine hydrate is introduced onto a 25-stage undamped perforated plate from the bottom of the separation tower, An acrylic acid-containing composition containing acrylic acid and 20 ppm by weight of p-methoxyphenol was obtained from the top of the column.

  72.07 g of the acrylic acid-containing composition, 293.06 g of ion-exchanged water, and 0.05 mol% of polyethylene glycol diacrylate (average added mole number of ethylene oxide: 8.2) based on the total monomers By mixing, an aqueous monomer solution having an acrylic acid concentration of 20 mass%, p-methoxyphenol of 4 ppm by mass, and a neutralization rate of 0 mol% was prepared.

  The whole amount of the monomer aqueous solution prepared above having a temperature of 20 ° C. was put into a polymerization vessel (a polypropylene cylindrical vessel having a volume of 1 L), and then nitrogen gas was blown to reduce the dissolved oxygen in the monomer aqueous solution to 1 ppm or less. did. Thereafter, the polymerization container was brought into an adiabatic state, and an aqueous solution containing 0.12 g of sodium persulfate as a polymerization initiator and an aqueous solution containing 0.0018 g of L-ascorbic acid were added. Thereafter, the polymerization of acrylic acid was allowed to proceed until 30 minutes had elapsed after the temperature of the aqueous monomer solution reached the peak temperature, to obtain a hydrogel polymer. The hydrogel polymer was subdivided into about 1 mm, and 62.5 g of a 48 mass% aqueous sodium hydroxide solution was added thereto to neutralize 75 mol% of the acid groups of the hydrogel polymer. The degree of polymerization of the hydrogel polymer calculated after this neutralization was 98.4%. Next, the hydrogel polymer is spread on a wire mesh having an opening of 850 μm, dried in hot air of a gas at 60 ° C. (dew point of 160 ° C.) for 60 minutes, pulverized by a vibration mill, and further having an opening of 850 μm. Classification was performed with a JIS standard sieve. The powder which passed the sieve by this classification was obtained as a water absorbent resin.

(Physical properties of water absorbent resin)
As for the physical properties of the water-absorbent resin, the absorption rate with respect to physiological saline was 50 times, the absorption rate with respect to artificial urine was 48 times, and the water-soluble component was 9% by mass. In addition, the measuring method of each physical property of a water absorbing resin was as follows.

(Absorption capacity for physiological saline)
The absorption ratio was calculated as follows in accordance with the method for calculating the absorption ratio under no load disclosed in US Pat. No. 5,164,459.
A tea bag type non-woven bag (40 mm × 150 mm) was charged with 0.2 g of a water absorbent resin, and then the opening of the non-woven bag was closed and sealed. This non-woven fabric bag was immersed in 100 g of physiological saline (0.9 mass% sodium chloride aqueous solution) having a temperature of 25 ± 3 ° C. for 30 minutes. After this immersion, drained. From the mass (W2) of the water absorbent resin and the nonwoven fabric bag before dipping in the physiological saline measured in this series of operations and the mass (W1) of the water absorbent resin and the nonwoven fabric bag after draining, The absorption capacity ((W1-W2) g / 0.2 g) of the water-absorbent resin with respect to physiological saline was calculated.

(Absorption capacity for artificial urine)
The absorption ratio was calculated as follows in accordance with the method for calculating the absorption ratio under no load disclosed in US Pat. No. 5,164,459.
Water-absorbing resin 0.2 g was put into a tea bag type non-woven bag (60 mm × 60 mm), and then the opening of the non-woven bag was closed and sealed. This nonwoven bag was immersed in 100 g of artificial urine having a temperature of 25 ± 3 ° C. for 60 minutes. After this immersion, the sample was drained at 250 G for 3 minutes using a centrifuge. From the mass (W4) of the water-absorbent resin and the non-woven fabric bag before dipping in artificial urine measured in this series of operations and the mass (W3) of the water-absorbent resin and the non-woven fabric bag after draining, the water absorption The absorption capacity ((W3-W4) g / 0.2g) of the synthetic resin with respect to artificial urine was calculated.
For artificial urine, artificial urine sold by Jayco (potassium chloride 2.0 g, sodium sulfate 2.0 g, ammonium dihydrogen phosphate 0.85 g, ammonium monohydrogen phosphate 0.15 g, calcium chloride 0 .19 g and a solution of 0.23 g of magnesium chloride dissolved in 1 L of distilled water).

(Water-soluble component)
500 mg of a water-absorbing resin was dispersed in 1000 ml of deionized water at room temperature and stirred for 16 hours with a magnetic stirrer, and then the swollen gel-like water-absorbing resin was filtered using filter paper (No. 6 manufactured by Toyo Roshi Kaisha, Ltd.). Next, the water-soluble component in the water-absorbent resin was determined by colloidal titration of the water-absorbent resin in the filtrate.

It is a schematic block diagram for demonstrating an example of the refiner | purifier in embodiment of this invention. It is a schematic block diagram for demonstrating the other example of the refiner | purifier in embodiment of this invention.

Claims (7)

  A purification step for removing phenol and / or 1-hydroxyacetone from the acrolein-containing composition; and an oxidation step for producing acrylic acid by oxidizing acrolein in the acrolein-containing composition after the purification step. A method for producing acrylic acid.   The method for producing acrylic acid according to claim 1, further comprising a dehydration step of dehydrating glycerin to produce acrolein before the purification step.   The method for producing acrylic acid according to claim 2, wherein in the dehydration step, glycerin is dehydrated in a gas phase.   The manufacturing method of an acrylic acid derivative which has the process of manufacturing acrylic acid using the manufacturing method of any one of Claims 1-3.   The method for producing an acrylic acid derivative according to claim 4, wherein the acrylic acid derivative is a water absorbent resin.   A purifier that removes phenol and / or 1-hydroxyacetone from the acrolein-containing composition; and an oxidation reactor that oxidizes acrolein in the acrolein-containing composition purified by the purifier to produce acrylic acid. An apparatus for producing acrylic acid, characterized by   A composition for producing acrylic acid containing acrolein, wherein the ratio (P / A) of the mass (A) of acrolein to the mass (P) of phenol is 0.020 or less, the mass (A) of acrolein and 1- A composition for producing acrylic acid, wherein the ratio (H / A) to the mass (H) of hydroxyacetone is 0.020 or less.

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