JP5130107B2 - Acrylic acid production method - Google Patents

Description

  The present invention relates to a method for producing acrylic acid in which acrolein is produced from glycerin and acrylic acid is produced from the acrolein.

  Biodiesel is attracting attention because it emits less carbon dioxide when used and can be used as a substitute for fossil fuels. Biodiesel is obtained by transesterification of vegetable oil, but it is known that glycerin is produced as a by-product in the reaction. As the demand and production of biodiesel increase year by year, the amount of glycerin produced as a by-product Has also increased. Under such a background, effective utilization of glycerin is desired.

  Acrolein is a compound obtained by intramolecular dehydration reaction of glycerin, and acrylic acid is a compound obtained by oxidizing acrolein. And it is possible to produce acrylic acid derivatives such as acrylic ester, polyacrylic acid, polyacrylic acid salt, water-absorbing resin from acrylic acid, and to produce acrylic acid from glycerin is a raw material for acrylic acid derivatives Therefore, the effective use of glycerin is realized, and the use range of by-products in biodiesel production is expanded, thereby increasing the economic value of biodiesel production.

  As described above, it is known to produce acrylic acid from glycerin (see, for example, Patent Document 1). In Patent Document 2, allyl alcohol, acetaldehyde, and propionaldehyde are by-produced during the production of acrolein from glycerin. Has been shown to do. In addition, in Patent Document 3 relating to the applicant's international patent application, a metal salt of phosphoric acid such as zinc salt of phosphoric acid or boron salt of phosphoric acid can be used as a catalyst when acrolein is produced from glycerin. It is disclosed.

By the way, when producing a resin such as a water-absorbing resin from acrylic acid, if acrylic acid containing propionic acid is used as a raw material, propionic acid that has been contained as an impurity of the resin causes the odor of the resin. In order to suppress this odor, removal of propionic acid from acrylic acid is one means, but it is also desired to produce acrylic acid while suppressing by-production of propionic acid. Moreover, in order to produce acrylic acid with a high yield from a certain amount of glycerin, it is desired that acrylic acid can be produced with high selectivity.
JP 2005-213225 A JP-A-6-217724 WO2007 / 119528

  In view of the above circumstances, an object of the present invention is to provide a method for producing acrylic acid from glycerin capable of obtaining acrylic acid while suppressing the by-production of propionic acid, and capable of producing acrylic acid with high selectivity. .

  As a result of intensive studies on reducing the production ratio of propionic aldehyde, which is a precursor of propionic acid, in order to reduce the production ratio of propionic acid to acrylic acid, the present inventors have made a boron salt of phosphoric acid and / or phosphoric acid. The present inventors have found that acrolein can be produced with a low propionaldehyde selectivity by coexisting a catalyst having a zinc salt with glycerin. In addition, when the catalyst was allowed to coexist with glycerin, a high selectivity of acrolein, which is a precursor of acrylic acid, was obtained. These findings led to the completion of the method for producing acrylic acid according to the present invention.

  That is, the method for producing acrylic acid according to the present invention comprises a catalyst having a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid and glycerin in the presence of glycerin to produce an acrolein-containing composition. And a step of oxidizing the acrolein obtained in the dehydration step to produce an acrylic acid-containing composition.

  The boron salt of phosphoric acid and / or the zinc salt of phosphoric acid in the catalyst of the dehydration step preferably has a crystal structure. When the boron salt and / or zinc salt has a crystal, adhesion of a carbonaceous substance to the surface of the salt can be suppressed, and the activity duration of the catalyst becomes long. In the dehydration step, it is preferable to dehydrate glycerin by a gas phase dehydration reaction in which the catalyst and glycerin gas are brought into contact with each other because this is an industrial dehydration step. The boron salt of phosphoric acid and the zinc salt of phosphoric acid in the catalyst are preferably 50% by mass or more.

  The method for producing acrylic acid according to the present invention preferably includes an acrolein purification step for removing phenol and / or 1-hydroxyacetone from the acrolein-containing composition between the dehydration step and the oxidation step. If this acrolein purification step is included, acrylic acid can be produced with higher yield.

  In addition, the method for producing acrylic acid according to the present invention includes an acrylic that removes propionic acid from the acrylic acid-containing composition by cooling the acrylic acid-containing composition and recovering the deposited acrylic acid after the oxidation step. It is preferred to have an acid purification step. By this purification step, an acrylic acid-containing composition with further reduced propionic acid is obtained.

  The catalyst according to the present invention is used in the dehydration step in the method for producing acrylic acid according to the present invention, and has a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid.

  Acrylic acid can be produced using the method for producing acrylic acid according to the present invention to produce an acrylic acid derivative. Here, the “acrylic acid derivative” is a compound using acrylic acid as a raw material, and examples thereof include acrylic acid esters, polyacrylic acid, polyacrylic acid salts, and water-absorbing resins.

  When propionaldehyde is oxidized, it becomes propionic acid, but according to the method for producing acrylic acid according to the present invention, since the ratio of propionaldehyde selectivity to acrolein selectivity generated in the dehydration step can be kept small, The ratio of the selectivity of propionic acid to the selectivity of acrylic acid produced by glycerin through the dehydration step and the oxidation step can also be reduced.

  In addition, according to the present invention, since the selectivity of acrolein produced in the dehydration step is high, the selectivity of acrylic acid produced when glycerin undergoes the dehydration step and the oxidation step is increased.

The present invention will be described based on an embodiment. The method for producing acrylic acid according to the present embodiment includes a dehydration process for producing an acrolein-containing composition from glycerin and an oxidation process for producing an acrylic acid-containing composition from acrolein obtained in the dehydration process. The method for producing acrylic acid according to the present embodiment obtains acrylic acid with a higher yield, so that the acrolein purification step removes by-products in the dehydration step from the acrolein-containing composition between the dehydration step and the oxidation step. Have In addition, the acrylic acid production method of the present embodiment is an acrylic that recovers the deposited acrylic acid by cooling the acrylic acid-containing composition after the oxidation step in order to obtain an acrylic acid-containing composition having a smaller amount of propionic acid. It has an acid purification step.
Hereinafter, each process is demonstrated in order of a process.

(Dehydration process)
In the dehydration step, glycerin and a catalyst (hereinafter, the catalyst in the dehydration step may be referred to as “catalyst (I)”) are used to produce acrolein by an intramolecular dehydration reaction of glycerin. In the dehydration reaction, one or two or more by-products selected from propionic acid, 1-hydroxyacetone, phenol and the like are also generated together with acrolein. The “acrolein-containing composition” in the present embodiment contains acrolein and its by-products.

  The catalyst (I) is not particularly limited as long as it has a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid as a catalytically active component. The more active component contained in the catalyst (I), the more suitable it is for industrial production of acrylic acid. Therefore, when the total amount of the catalyst (I) used is 100% by mass, boron phosphate contained in this catalyst (I) The salt and zinc salt of phosphoric acid are preferably 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

The catalyst (I) may be one in which a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid is supported on a carrier. Examples of the carrier at this time include inorganic oxides and composite oxides such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , and ZrO ₂ ; crystalline metallosilicates such as zeolite; metals such as stainless steel and aluminum; . Further, the shape of the catalyst (I) is not particularly limited, and is, for example, a spherical shape, a column shape, a ring shape, a bowl shape, a honeycomb shape, or a sponge shape.

The boron salt of phosphoric acid is not particularly limited, and the catalyst (I) may contain one or more of the salts. Examples of the boron salt of phosphoric acid include BPO ₄ , B ₄ (P ₂ O ₇ ) ₃ , B ₅ (P ₃ O ₁₀ ) ₃ , and B ₂ P ₄ O ₁₀ .

  The boron salt of phosphoric acid preferably has a crystal structure. In the case of having this crystal structure, adhesion of the carbonaceous substance to the boron salt of phosphoric acid, which causes a decrease in the activity of the catalyst (I), can be suppressed even in the continuous dehydration reaction of glycerol. The crystal structure is not particularly limited, and is, for example, a tetragonal crystal.

The zinc salt of phosphoric acid is not particularly limited as long as it is a salt with phosphoric acid, and the salt may be one kind or two or more kinds. Examples of the zinc salt of phosphoric acid include Zn ₃ (PO ₄ ) ₃ , Zn ₂ P ₂ O ₇ , Zn ₅ (P ₃ O ₁₀ ) ₂ , and Zn ₃ P ₄ O ₁₀ .

  It is also preferable that the zinc salt of phosphoric acid has a crystal structure. Even in the case of having this crystal structure, adhesion of the carbonaceous substance to the zinc salt of phosphoric acid, which causes a decrease in the activity of the catalyst (I), can be suppressed even in the continuous dehydration reaction of glycerol. The crystal structure is not particularly limited, and is, for example, monoclinic or orthorhombic.

  Boron salts of phosphoric acid and zinc salts of phosphoric acid are commercially available, and these commercially available compounds may be used in the dehydration step. Further, a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid obtained by a known catalyst preparation method such as a precipitation method, a coprecipitation method, a sol-gel method, or a hydrothermal synthesis method can also be used in the dehydration step. The coprecipitation method is a method in which two or more kinds of ions are simultaneously precipitated, and is preferable in terms of easy control of the precipitation composition.

More specific examples for preparing the boron salt of phosphoric acid include H ₃ BO ₃ , HBO ₃ , H ₄ B ₂ O ₄ , H ₃ BO ₂ , H ₃ BO, (NH ₄ ) ₂ O · 5B. _From one or more boron source compounds selected from ₂ O ₃ .8H ₂ O, etc., and H ₃ PO ₄ , H ₂ P ₂ O ₇ , H ₅ P ₃ O ₁₀ , H ₆ P ₄ O _10, etc. An aqueous solution prepared using one or more selected phosphoric acids may be heated. The amount of boron source compound used and the amount of phosphoric acid used are not particularly limited.

More specific examples for preparing the other zinc salt of phosphoric acid include inorganic acids such as Zn (NO ₃ ) ₂ , ZnCO ₃ , Zn (OH) ₂ , ZnCl ₂ , Zn (CH ₃ COO) ₃ One or more zinc source compounds selected from salts and organic acid salts and selected from H ₃ PO ₄ , H ₂ P ₂ O ₇ , H ₅ P ₃ O ₁₀ , H ₆ P ₄ O _10, etc. One or two or more phosphoric acids may be used to form a zinc salt of phosphoric acid in water. The amount of zinc source compound used and the amount of phosphoric acid used are not particularly limited.

  In order to form the zinc salt of phosphoric acid, for example, (1) a coprecipitation method in which an alkaline compound is added to an aqueous solution prepared using a zinc source compound and phosphoric acid to produce a zinc salt of phosphoric acid; 2) A sol-gel method in which phosphoric acid is added after an alkaline compound is added to an aqueous solution prepared using a zinc source compound to form a zinc hydroxide in the aqueous solution. Here, the “alkaline compound” is a compound in which the solvent becomes alkaline when dissolved in water; ammonia; methylamine, ethylamine, n-propylamine, isopropylamine, sec-butylamine, dimethylamine, diethylamine, Aliphatic amines such as trimethylamine and triethylamine; alicyclic amines such as cyclohexylamine; alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; pyridine; ammonium carbonate; urea; Alkali metal hydroxide or the like may be used as the alkaline compound, but if the alkali metal remains in the catalyst (I), the performance of the catalyst (I) may be adversely affected. As preferred, ammonia is particularly preferred.

  The addition amount of the alkaline compound may be an amount that makes the pH of the aqueous solution to be added 2 to 13, preferably an amount that makes the pH 4 to 11, and more preferably an amount that makes the pH 7 to 9. In addition of the alkaline compound, the alkaline compound may be gradually added at a constant rate, or the alkaline compound may be added all at once, but in order to make the particle size of the zinc salt of phosphoric acid uniform, the former It is preferable to add gradually. The temperature of the aqueous solution at the time of adding the alkaline compound is not particularly limited, but when a volatile alkaline compound is selected, the pH adjustment difficulty due to volatilization of the compound and the reproducibility of the zinc salt of phosphoric acid are considered. If it does, 1-50 degreeC will be normal and 20-40 degreeC is good. After the addition of the alkaline compound is completed, it is preferably left as it is in order to make the size of the salt particles uniform.

  In order to obtain a boron salt of phosphoric acid having a crystal structure or a zinc salt of phosphoric acid, the salt is preferably calcined. However, if the salt contains a large amount of ammonium nitrate or the like, the salt is used as it is at the firing temperature atmosphere. If placed on the gas, gas such as ammonium nitrate may be scattered and explode. Therefore, in order to reduce the gas generated during firing, it is preferable to place the salt before firing in an atmosphere at a temperature lower than the firing temperature. In order to reduce the gas, for example, the salt before firing may be placed in an air atmosphere at 150 to 230 ° C or an inert gas atmosphere at 150 to 350 ° C.

  There is a general tendency that crystallization progresses as the firing temperature is higher, and there is a general tendency that crystallization progresses as the firing time is longer. If there is an extreme change in the yield of acrolein in the intramolecular dehydration reaction of glycerin, acrylic acid cannot be produced stably, so if the firing temperature and time have no extreme change in crystal structure, the temperature and time Is not particularly limited. The firing conditions are, for example, 500 to 1500 ° C. for 3 to 15 hours in air, 600 to 1400 ° C. and 3 to 10 hours, and preferably 700 to 1200 ° C. and 3 to 5 hours.

  In the case where a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid is supported on a carrier, for example, (1) a liquid containing a raw material of boron salt of phosphoric acid and / or zinc salt of phosphoric acid is used as the carrier. Impregnation method of impregnation and heating, (2) precipitation of boron salt of phosphoric acid and / or zinc salt of phosphoric acid in liquid containing carrier, or boron salt of phosphoric acid and / or zinc salt of phosphoric acid Examples thereof include a precipitation method in which a carrier is added to the precipitated liquid, and (3) a kneading method in which a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid is mixed with a carrier.

  The glycerin used is not particularly limited, and may be either purified glycerin or crude glycerin. This glycerin is produced by transesterification of vegetable oils such as palm oil, palm kernel oil, coconut oil, soybean oil, rapeseed oil, olive oil and sesame oil; animal oils such as fish oil, beef tallow, lard It may be glycerol derived from natural resources such as glycerol produced by transesterification. Further, glycerin chemically synthesized from ethylene, propylene or the like may be used.

  In the dehydration step, any of a gas phase dehydration reaction caused by contact between the glycerin gas and the catalyst (I) and a liquid phase dehydration reaction caused by contact between the liquid glycerin and the catalyst (I) may occur. Hereinafter, a method for producing acrolein using a gas phase dehydration reaction excellent in industrial productivity of acrolein will be described as an example.

  In the gas phase dehydration reaction of glycerin, the glycerin-containing gas and catalyst (I) are brought into contact in a reactor arbitrarily selected from a fixed bed reactor, a moving bed reactor, a fluidized bed reactor and the like.

  The glycerin concentration in the glycerin-containing gas is not particularly limited, but if it is necessary to adjust the glycerin concentration in the glycerin-containing gas, select from condensable and non-condensable gases that do not adversely affect the dehydration reaction that produces acrolein from glycerin The glycerol concentration is adjusted by including one or two or more kinds of gases as a diluent gas in the glycerol-containing gas. In order to prepare a glycerin-containing gas containing a dilution gas, gasification of a solution of glycerin and a dilution gas component or mixing of glycerin gas and a dilution gas may be performed.

  In order to increase the selectivity and yield of acrolein in the dehydration process and reduce the amount of carbonaceous material adhering to the surface of the catalyst (I) to improve the life of the catalyst (I), a glycerin-containing gas It is preferable to adjust the partial pressure of the glycerin gas therein. In order to improve the yield and the like, the partial pressure of glycerin gas is preferably 30 kPa or less, preferably 25 kPa or less, more preferably 20 kPa or less, and further preferably 15 kPa or less. Considering only the improvement in the yield of acrolein and the life of the catalyst (I), the lower the partial pressure of glycerin, the better. However, when the pressure of the glycerin-containing gas (total pressure) is reduced to achieve the partial pressure, In addition, a reactor having high airtightness and pressure-resistant resistance and a large pressure reducing device are required, and it is not economical when the partial pressure is reduced by using a large amount of dilution gas. From this economical viewpoint, the partial pressure of glycerin gas is preferably 0.01 kPa or more, preferably 1.0 kPa or more, and more preferably 2.0 kPa or more. The partial pressure of glycerin gas is the pressure at the reactor inlet, and the partial pressure when dilution gas is included in the glycerin-containing gas is the glycerin-containing gas pressure (total pressure) and the molarity of glycerin at the reactor inlet. It is a value calculated based on the concentration (mol%).

  Even if the pressure of the glycerin-containing gas is not arbitrarily set, acrolein is generated in the dehydration step. In general, the pressure is appropriately set from the balance between the gas tightness and pressure resistance performance of the reactor and the catalyst (I) performance, and the pressure of the glycerin-containing gas is preferably 0.01 kPa to 1 MPa. 1 kPa to 500 kPa is preferable, 1 kPa to 300 kPa is more preferable, and 1 kPa to 200 kPa is still more preferable.

  When adjusting the glycerin concentration of the glycerin-containing gas using a dilution gas, the condensable gas that can be used as the dilution gas is a gas of a compound having a boiling point higher than that of acrolein and 200 ° C. or less under normal pressure conditions, For example, water vapor; gas of alkane compound such as hexane, heptane, octane, cyclohexane; gas of aromatic compound such as benzene, toluene, xylene, mesitylene, ethylbenzene; When water vapor is selected, the life of the catalyst (I) and the yield of acrolein are improved. In order to reduce the energy consumption when heating and / or cooling the glycerin-containing gas, and to reduce the separation cost of acrolein and the condensable gas, the concentration of the condensable gas in the glycerin-containing gas should be 80 mol% or less. It is preferably 40 mol% or less, more preferably 10 mol% or less. In addition, the partial pressure of the condensable gas is preferably 5 times or less the partial pressure of the glycerin gas from the viewpoint of energy required for generating the gas and condensing the condensable gas flowing out of the reactor and wastewater treatment. 4 times or less is more suitable, and 1 time or less is most suitable.

  The non-condensable gas used as the dilution gas of the glycerin-containing gas is a compound or a single gas having a boiling point of 0 ° C. or lower under normal pressure conditions, for example, an oxygen-containing gas such as nitrogen gas, carbon dioxide gas, air, Examples include noble gases such as helium. When oxygen is selected, the amount of carbonaceous material deposited on the surface of the catalyst (I) is reduced. The concentration of the non-condensable gas in the glycerin-containing gas is preferably 40 mol% or less, and while suppressing the energy consumption when the glycerin-containing gas is heated and / or cooled, the concentration of the acrolein during liquefaction recovery of acrolein is reduced. In order to reduce scattering loss, the concentration of the non-condensable gas in the glycerin-containing gas should be 10 mol% or less, preferably 8 mol% or less, and more preferably 5 mol% or less. Further, the partial pressure of the non-condensable gas is preferably not more than twice the partial pressure of the glycerin gas, preferably not more than 1 time, and more preferably not more than 0.5 times. When oxygen is used as a diluent gas, the amount of oxygen in the glycerin-containing gas is 20 mol% or less (more preferably 15 mol% or less) in order to avoid a decrease in acrolein yield due to combustion reaction, And an amount that is 3.5 times or less of the glycerin gas partial pressure, whichever is lower, is preferable.

Glycerin-containing gas flow into the reactor, glycerin-containing gas flow rate per unit catalyst (I) volume (flow rate: GHSV) is represented by, 10～30000Hr ^-1 it is usually good 30～20000Hr ^-1, 50-12000hr < ^-1 > is preferable, 70-10000hr < ^-1 > is more preferable, 100-5000hr < ^-1 > is still more preferable. In order to produce acrolein economically and with high efficiency, 3000 hr ⁻¹ or less is preferable. The GHSV of the glycerin-containing gas is determined based on the flow rate of the glycerin-containing gas itself at the reactor inlet, and differs from the glycerin gas GHSV described below in the determination method (the glycerin in the glycerin-containing gas is When it is 100 mol%, GHSV of glycerin gas described later is employed.)

GHSV of glycerin gas is (mass ratio of glycerin in glycerin-containing gas) × (mass of glycerol-containing gas per 1 L of catalyst (I) and 1 hour) × (volume of ideal gas in standard state) / (molecular weight of glycerin) ) Is a calculated value. For example, when a glycerin-containing gas having a glycerin content of 90% by mass is supplied into a reactor equipped with 1 L of catalyst (I) at a flow rate of 1000 g · hr ⁻¹ , the GHSV of the glycerin gas is 0.9 × 1000 g · hr is a ^{-1 · L -1 × 22.4L ÷ 92.06g} = 219hr -1. The GHSV of this glycerin gas is usually from 70 to 3650 hr ^{−1 in} consideration of economic aspects such as miniaturization of the reactor, industrial (eg, catalyst (I) life, and acrolein production efficiency, good 2400hr ^-1, preferably 100~1200hr ^-1, more preferably 125~1200hr ^-1, 125~600hr ^-1 is more preferable.

  In the gas phase dehydration reaction of glycerin, if the reaction temperature is too low or too high, the yield of acrolein will be lowered. Therefore, the reaction temperature is preferably 200 to 500 ° C, and preferably 250 to 450 ° C. 300 to 450 ° C is more preferable, and 350 to 400 ° C is still more preferable. Here, the “reaction temperature” in the gas phase dehydration reaction means a set temperature of a heating medium or the like for controlling the temperature of the reactor.

  An acrolein-containing composition is obtained by gas phase dehydration reaction of glycerin. When it is necessary to temporarily recover acrolein in the acrolein-containing composition, for example, a method of liquefying acrolein by cooling or a method of absorbing acrolein in a solvent such as water may be used. Further, when the dilution gas is exhausted in this recovery, a part or all of the exhausted dilution gas may be reused as the dilution gas for the glycerin-containing gas introduced into the reactor.

  In the intramolecular dehydration reaction of glycerin, unreacted glycerin may be contained in the obtained acrolein-containing composition (the same applies to both gas phase dehydration reaction and liquid phase dehydration reaction). If the phase dehydration reaction is continued, the activity of the catalyst (I) is reduced to an extent that is not industrially suitable.

  Unreacted glycerin is preferably recovered from the acrolein-containing composition and used again in the dehydration step. By this reuse, the amount of acrolein obtained from a certain amount of glycerol can be increased, and the amount of acrylic acid obtained from a certain amount of glycerol can also be increased. Glycerin has a high boiling point among the compounds contained in the acrolein-containing composition, and thus can be easily recovered by condensation or the like.

  Regarding the decrease in the activity of the catalyst (I), the catalyst activity can be increased to a practical level by regenerating the catalyst (I). When the regeneration gas and the catalyst (I) are brought into contact with each other at a high temperature, the carbonaceous material adhering to the surface of the catalyst (I) can be removed to regenerate the catalyst (I).

  The “regeneration gas” is a gas containing an oxidizing gas, and the oxidizing gas is, for example, oxygen or air containing oxygen. In addition, a gas that is inert in the catalyst regeneration reaction such as nitrogen, carbon dioxide, and water vapor may be included in the regeneration gas, and when sudden heat generation is a concern due to contact between oxygen and the catalyst (I). In order to suppress the rapid heat generation, it is recommended to include an inert gas in the regeneration gas.

  The method for bringing the regeneration gas into contact with the catalyst (I) is a method in which the regeneration gas is brought into contact with the catalyst (I) taken out from the reactor; the regeneration gas is circulated in the reactor after the dehydration reaction of glycerol. The method; etc. are not particularly limited. The latter method in which the regeneration gas is circulated in the reactor is preferable because the removal of the catalyst (I) from the reactor and the recharging of the catalyst (I) into the reactor can be omitted.

  The temperature at the time of contact with the regeneration gas is appropriately set to a temperature at which the carbonaceous material can be removed. For example, when the regeneration gas is circulated through the reactor, the temperature of the heating medium for controlling the temperature of the reactor is preferably 330 ° C. or higher, preferably 350 ° C. or higher, and the upper temperature limit is the catalyst (I) Is a temperature at which no thermal degradation occurs.

(Acrolein purification process)
The acrolein-containing composition obtained in the dehydration step includes a by-product of the intramolecular dehydration reaction of acrolein and glycerin. Propionaldehyde may be included as a by-product, and other by-products may include phenol, 1-hydroxyacetone, allyl alcohol, and the like. In the acrolein purification step, phenol and / or 1-hydroxyacetone is removed from the acrolein-containing composition. By performing this removal, the yield of acrylic acid can be further increased. When 1-hydroxyacetone is removed, the by-product of acetic acid in the oxidation process is suppressed.

Since the yield of acrylic acid is increased by removing phenol, the larger the amount of phenol removed, the better. The amount of phenol after removal can be expressed as a ratio (Ph / A) of the mass (A) of acrolein to the mass (Ph) of phenol, with Ph / A being 0.020 or less, and 0.010 or less. Preferably, it is more preferably 0.005 or less. Although it is preferable that the amount of phenol to be removed is large, the problem that the amount of acrolein loss increases and the acrolein production step becomes complicated are likely to occur as the amount of removal is increased. Considering this, Ph / A is preferably 1 × 10 ⁻⁹ or more, preferably 1 × 10 ⁻⁷ or more, more preferably 1 × 10 ⁻⁵ or more.

Moreover, since the yield of acrylic acid is increased by removing 1-hydroxyacetone, the larger the amount of 1-hydroxyacetone removed, the better. The amount of 1-hydroxyacetone after removal is expressed by the ratio (H / A) of the mass (A) of acrolein and the mass (H) of 1-hydroxyacetone, and H / A is 0.020 or less. Good, preferably 0.010 or less, and more preferably 0.005 or less. In the removal of 1-hydroxyacetone, if the same problem of loss of acrolein as in the above phenol removal occurs, H / A may be 1 × 10 ⁻⁹ or more, preferably 1 × 10 ⁻⁷ or more, More preferably, it is 1 × 10 ⁻⁵ or more.

  Utilizing the difference in boiling point between acrolein (boiling point: about 53 ° C.), phenol (boiling point: about 182 ° C.), and 1-hydroxyacetone (boiling point: about 146 ° C.), phenol and / or 1-hydroxyacetone from the acrolein-containing composition. Can be removed. For this purpose, for example, a method in which liquid acrolein is treated with a distillation column to fractionate acrolein having a lower boiling point than that of the object to be removed, or a gaseous acrolein is treated in a coagulation tower to remove a boiling point higher than that of acrolein. It is preferable to employ a method of agglomerating the product or a method of injecting gas into acrolein introduced into the transpiration tower to vaporize acrolein having a boiling point lower than that of the object to be removed. Moreover, acrolein (melting point: about −87 ° C.), phenol (melting point: about 43 ° C.), 1-hydroxyacetone (melting point: about −17 ° C.), such as removing cooling precipitates of phenol and / or 1-hydroxyacetone Phenol and / or 1-hydroxyacetone may be removed from the acrolein-containing composition using the difference in melting point. It should be noted that propion from an acrolein-containing composition by utilizing the difference in boiling point or the melting point difference between acrolein (boiling point: about 53 ° C, melting point: -87 ° C) and propionaldehyde (boiling point: about 48 ° C, melting point: about -81 ° C). Although it is possible to remove aldehydes, the difference in boiling point and melting point between them is small, so that the amount of loss of acrolein increases.

(Oxidation process)
In the oxidation step, an acrylic acid-containing composition is produced by oxidizing acrolein in the acrolein-containing composition. The oxidation step of the present embodiment is based on a known vapor phase oxidation reaction of acrolein which is industrially suitable.

  In order to produce acrylic acid by oxidation of acrolein, a gas containing an acrolein-containing composition (hereinafter sometimes referred to as “acrolein-containing gas”) and a catalyst (hereinafter referred to as “catalyst (II)” in the oxidation step). Can be coexisted in an oxidation reactor arbitrarily selected from a fixed bed reactor, a moving bed reactor, a fluidized bed reactor, etc., and acrolein can be vapor-phase oxidized at 200 to 400 ° C. Is preferred. Propionic acid is produced from propionaldehyde with the acrolein oxidation reaction, but in this embodiment, the amount of propionaldehyde contained in the acrolein-containing composition is kept low, so propion The amount of acid produced is small.

  The catalyst (II) is not particularly limited as long as it is a known catalyst used for producing acrylic acid by a catalytic gas phase oxidation method using acrolein and molecular oxygen or a gas containing molecular oxygen. 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 (II), a molybdenum-vanadium catalyst in which molybdenum and vanadium are main constituent metals is preferable. Further, the catalyst (II) 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 amount of oxygen added to the acrolein-containing gas used in the production of acrylic acid is appropriately set because the amount of oxygen added is excessive, because there is a risk of combustion and risk of explosion.

  In order to recover the acrylic acid-containing composition gas produced by the gas phase oxidation reaction, it is preferable that the gas is cooled or absorbed in a solvent such as water.

(Acrylic acid purification process)
In the acrylic acid purification step, propionic acid is removed from the acrylic acid-containing composition obtained in the oxidation step. The amount of propionic acid contained in the acrylic acid-containing composition obtained in the oxidation step can be suppressed because the catalyst (I) is used in the dehydration step, but when a smaller amount of propionic acid is required In addition, propionic acid is removed in the acrylic acid purification step.

  The removal of propionic acid from the acrylic acid-containing composition is performed by cooling the composition and recovering the acrylic acid that precipitates before propionic acid. Since the boiling points of propionic acid (boiling point: about 141 ° C.) and acrylic acid (boiling point: about 141 ° C.) are almost the same, it is difficult to remove propionic acid from the acrylic acid-containing composition using the boiling point difference. However, there is a large difference between the melting points of propionic acid (melting point: about −21 ° C.) and acrylic acid (melting point: 12 ° C.), and recovery of acrylic acid from the acrylic acid-containing composition (propionic acid removal) is easy. is there. The temperature for cooling the acrylic acid-containing composition when removing propionic acid is preferably −18 to 10 ° C., preferably −18 to 4 ° C., and more preferably −18 to 0 ° C. In addition, when impurities other than propionic acid such as acetic acid, acrolein, and water are contained in the acrylic acid-containing composition, the impurities are removed by a known method such as distillation, and then propionic acid is removed by cooling. Is preferred.

  The method for producing acrylic acid according to this embodiment is as described above. 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.

(Experimental example)
Below, a part of experimental example which came to discover the manufacturing method of the acrolein which concerns on this invention is shown.

  Various catalysts (I) were prepared, and acrolein was produced using the catalyst (I). Details of the analysis methods in Experimental Examples 1 to 4 and Comparative Experimental Examples 1 to 29, the method of measuring the amount of carbonaceous material on the surface of the catalyst (I), the method of preparing the catalyst (I), and the production of acrolein (dehydration step) Is as follows.

(Fluorescence X-ray (XRF) analysis)
Using a fluorescent X-ray analyzer “PW2404” manufactured by PHILIPS, metal atoms (M atoms) and phosphorus atoms in the catalyst (I) were analyzed by the glass bead method. Quantification of M atom and phosphorus atom was performed using a calibration curve prepared using a standard sample prepared in advance.

(X-ray diffraction (XRD) analysis)
Using a powder X-ray diffractometer “RINT-TTRIII” manufactured by Rigaku Corporation, the crystal structure of the catalyst (I) was analyzed under the following conditions.
X-ray source: Cu
Filter: Non-use tube voltage: 50kV
Tube current: 300mA
Divergent slit: 1/3 °
Scattering slit: 1/2 °
Receiving slit: Open scanning range: 5-90 °
Sampling width: 0.02 °
Scan speed: 3.000 ° / sec

(Measurement of amount of carbonaceous material)
Using thermogravimetric-differential thermal analysis (TG-DTA), the catalyst (I) was placed in an air stream, the temperature was raised from room temperature to 900 ° C. at a rate of 10 ° C./min, and the mass change of the catalyst (I) was acrolein. It was measured as the amount of carbonaceous material attached to the catalyst (I) during production.

(Preparation of catalyst (I))
Catalyst (I) was prepared by the following coprecipitation method, sol-gel method, reflux-concentration, or calcination of a commercially available metal phosphate. Regarding the type of metal atom source compound (M source compound) used in the preparation of catalyst (I); the amount of metal atom source compound, phosphoric acid, and aqueous ammonia used; the calcination temperature in the preparation of catalyst (I); As described in Tables 1-1 and 1-2 below. Also, P / M calculated from the XRF analysis result of the prepared catalyst (I) (P: mole number of phosphorus atom, M: mole number of metal atom); catalyst composition and crystal structure as a result of XRD analysis; These are shown in Tables 1-1 and 1-2 below.

Preparation of catalyst (I) by sol-gel method:
While stirring this aqueous solution in a 10 mass% metal atom source compound aqueous solution at 30 ° C, 28 mass% aqueous ammonia was kept constant for 3 hours using a pump for high performance liquid chromatography ("L7110" manufactured by Hitachi, Ltd.). It was dropped at a dropping speed. The solution after dropping was allowed to age for 15 hours with stirring to obtain a catalyst precursor solution A. While stirring this solution A to the catalyst precursor solution A, an 85 mass% H ₃ PO ₄ aqueous solution was dropped at a constant rate over 3 hours using a high-performance liquid chromatograph pump, and then stirred while stirring 15 The catalyst precursor solution B was obtained by allowing to stand for aging for aging. The catalyst precursor solution B was sol or gelled. The catalyst precursor solution B was dehydrated under conditions of 0.005 MPa and 60 ° C., and then dried under conditions of 120 ° C. and 10 hours in an air atmosphere. Next, by placing the dried product in a nitrogen atmosphere at 300 ° C. for 10 hours, ammonium nitrate was thermally decomposed and separated from the dried product. Thereafter, the dried product was fired in air for 5 hours to obtain a metal salt crystal of phosphoric acid. The crystals were pulverized and passed through a sieve having an aperture of 0.7 to 2.0 mm to obtain catalyst (I).

Preparation of catalyst by coprecipitation method:
A 10% by mass metal atom source compound and 85% by mass phosphoric acid aqueous solution were mixed to prepare a transparent mixed solution at 30 ° C. While stirring, 28% by mass of aqueous ammonia was dropped at a constant rate over 3 hours using a high-performance liquid chromatograph pump (precipitate was formed from the beginning of the dropping). The solution after dropping was left to age for 15 hours with stirring, and the resulting precipitate was separated by filtration and dried under conditions of 120 ° C. and 10 hours in an air atmosphere. Next, by placing the dried product in a nitrogen atmosphere at 300 ° C. for 10 hours, ammonium nitrate was thermally decomposed and separated from the dried product. Thereafter, the dried product was fired in the air for 5 hours to obtain a metal salt crystal of phosphoric acid. The crystal was pulverized and passed through a sieve having an aperture of 0.75 to 2.00 mm to obtain catalyst (I).

Preparation of catalyst (I) by reflux-concentration:
A mixed solution of a 10 mass% metal atom source compound aqueous solution and an 85 mass% phosphoric acid aqueous solution was refluxed at 90 ° C. for 2 hours. The mixed liquid after refluxing was dehydrated under conditions of 0.005 MPa and 60 ° C., and then dried under conditions of 120 ° C. and 24 hours in an air atmosphere. Next, the dried product was fired in air for 5 hours to obtain a metal salt crystal of phosphoric acid. The crystals were pulverized and passed through a sieve having an aperture of 0.7 to 2.0 mm to obtain catalyst (I).

Preparation of catalyst (I) by calcination of commercial phosphate:
A commercially available phosphate was fired in air for 5 hours to obtain a metal salt crystal of phosphoric acid. The crystals were pulverized and passed through a sieve having an aperture of 0.7 to 2.0 mm to obtain catalyst (I).

(Manufacturing of acrolein (dehydration process))
A stainless steel reaction tube (inner diameter 10 mm, length 500 mm) filled with 15 ml of catalyst (I) was prepared as a fixed bed reactor, and this reactor was immersed in a 360 ° C. molten salt bath. Then, after flowing nitrogen through the reactor at a flow rate of 62 ml / min for 30 minutes, 80 mass% glycerin-containing gas (glycerin-containing gas composition: glycerin 27 mol%, water 34 mol%, nitrogen 39 mol%) was added to GHSV 640 hr. The flow rate was ^-1 . The acrolein-containing composition gas flowing out from the reactor was absorbed in water for 30 minutes before the passage of a predetermined time after the glycerin-containing gas was circulated in the reactor, and the compounds in the water were quantitatively analyzed. In this analysis, gas chromatography (GC) equipped with a FID was used, and an internal standard method was adopted.

  In addition, about the measurement of the carbonaceous substance on the surface of the catalyst (I) using TG-DTA, the catalyst (I) after 7 hours from the start of circulation of the glycerin-containing gas was used as a sample.

  The conversion rate of glycerin (GLY conversion rate) was calculated based on the following formula (1), and the adhesion amount of the carbonaceous material on the surface of the catalyst (I) was calculated based on the following formula (2). Selectivities of acrolein (ACR), propionaldehyde (PARD), 1-hydroxyacetone (HDAC), and phenol (PhOH) were calculated based on the following formula (3). The yield of acrolein (ACR yield) was calculated based on the following formula (4).

  Tables 2, 3-1, 3-2, 4-1, and 4-2 show conversion rates of glycerin (GLY conversion rate) and the like.

  When comparing the experimental examples in Tables 4-1 and 4-2 with the comparative experimental examples, (experimental selectivity of propionaldehyde (PARD)) / (selectivity of acrolein (ACR)) × 100, most of the experimental examples were compared. Lower than the experimental example. This means that if boron salt of phosphoric acid and / or zinc salt of phosphoric acid is used as catalyst (I), the selectivity of propionaldehyde, which is a precursor of propionic acid, is significantly lower than that of acrolein. It shows that it can be manufactured. That is, according to the method for producing acrylic acid according to the present invention, the ratio of the selectivity of propionic acid to the selectivity of acrylic acid to be generated can be reduced.

  Further, when comparing the experimental examples of Tables 4-1 and 4-2 with the comparative experimental examples, the selectivity of acrolein is higher than most comparative experimental examples. This indicates that the selectivity of acrylic acid can be increased by using a boron salt of phosphoric acid and / or a zinc salt of phosphoric acid as the catalyst (I).

  Next, in the method for producing acrolein according to the present invention, if an acrolein purification step for removing phenol and / or 1-hydroxyacetone from the acrolein-containing composition is provided between the dehydration step and the oxidation step, higher yield is obtained. Some of the experimental examples that led to the finding that acrylic acid can be produced at a rate are shown below.

  Acrylic acid was prepared using catalyst (II) and an acrolein-containing composition. Details of production of catalyst (II) and acrylic acid (oxidation step) in Experimental Example 5 and Comparative Experimental Examples 30 to 32 are as follows.

(Preparation of catalyst (II))
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 these two liquids were mixed, 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 (II) precursor. This catalyst (II) precursor was calcined at 400 ° C. for 6 hours to prepare catalyst (II). In addition, the metal composition of the catalytically active component supported on the carrier in the catalyst (II) is Mo ₁₂ V _6.1 W ₁ Cu _2.3 Sb _1.2 .

(Manufacture of acrylic acid (oxidation process))
A stainless steel reaction tube filled with 20 ml of catalyst (II) was prepared as a fixed bed reactor, and an acrolein-containing composition gas was circulated at a flow rate of GHSV 2000 hr ⁻¹ . And the acrylic acid containing composition gas which flowed out from the fixed bed reactor between the start of distribution for 60 to 80 minutes was collected, and this component was analyzed by gas chromatography. In addition, the acrolein-containing composition gas contains 33.36 parts by volume of water vapor (Experimental Example 5); 33.18 parts by volume of water vapor and 0.18 parts by volume of phenol (Comparative Experimental Example 30); 1-hydroxyacetone 0.36 part by volume (Comparative Experimental Example 31); or water vapor 33.00 part by volume, and allyl alcohol 0.36 part by volume (Comparative Experimental Example 32); A gas having 10.44 and 1.8 parts by volume of acrolein as components was used.

  The conversion rate of acrolein (ACR conversion rate) was calculated based on the following formula (5). The yields of acrylic acid (AA) and acetic acid (AcOH) were calculated based on the following formulas (6) and (7).

  Table 5 shows the results of Experimental Example 5 and Comparative Experimental Examples 30 to 32.

  As shown in Table 5, when an acrolein-containing composition gas containing phenol (Comparative Experimental Example 30) or 1-hydroxyacetone (Comparative Experimental Example 31) was used, rather than Experimental Example 5 in which these compounds were not added, The conversion rate of acrolein (ACR conversion rate) and the yield of acrylic acid (AA) are poor. From this, it can be said that if an acrolein purification step for removing phenol and / or 1-hydroxyacetone from the acrolein-containing composition is provided between the dehydration step and the oxidation step, the yield of acrylic acid is increased.

  From Experimental Example 5 and Comparative Experimental Example 31, it can be said that when 1-hydroxyacetone is removed, the by-product of acetic acid can be suppressed.

Claims (8)

A dehydration step of producing an acrolein-containing composition by dehydrating glycerin in the presence of glycerol with a catalyst having a zinc salt of phosphoric acid having a monoclinic or orthorhombic crystal structure ;
An oxidation step of oxidizing an acrolein obtained in the dehydration step to produce an acrylic acid-containing composition. The method for producing acrylic acid according to claim 1, wherein in the dehydration step, glycerin is dehydrated by a gas phase dehydration reaction in which the catalyst and glycerin gas are brought into contact with each other. The zinc salt of lapis lazuli phosphate put into the catalyst dehydration step, method for producing acrylic acid according to claim 1 or 2 is at least 50 mass%. The production of acrylic acid according to any one of claims 1 to 3 , further comprising an acrolein purification step for removing phenol and / or 1-hydroxyacetone from the acrolein-containing composition between the dehydration step and the oxidation step. Method. Any one of Claims 1-4 which has an acrylic acid refinement | purification process which removes propionic acid from an acrylic acid containing composition by collect | recovering the acrylic acid which precipitated after cooling the acrylic acid containing composition after the said oxidation process. 2. A method for producing acrylic acid according to item 1. A catalyst used in the dehydration step as claimed in any one of claims 1 to 5 catalyst having a zinc salt of-phosphate having a monoclinic or orthorhombic crystal structure. The manufacturing method of an acrylic acid derivative which has the process of manufacturing acrylic acid using the manufacturing method of acrylic acid of any one of Claims 1-5 . The method for producing an acrylic acid derivative according to claim 7 , wherein the acrylic acid derivative is a water absorbent resin.