KR20190042095A - METHOD FOR MANUFACTURING METHACRYLIC ACID AND METHOD FOR MANUFACTURING THE SAME, - Google Patents

Abstract

A catalyst for the production of methacrylic acid having a high yield of methacrylic acid. A catalyst for the production of methacrylic acid, which comprises at least phosphorus, molybdenum and vanadium-containing heteropoly acid salts, which is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, In the X-ray diffraction pattern using the Cu-K? Line of the catalyst for the production of methacrylic acid which was allowed to stand for 12 hours under an environment where the humidity was kept at 90%, the absolute value of the peak intensity I ₀ of the (222) plane attributed to the cubic structure of the heteropoly acid salt (I ₁ / I ₀ ) of the absolute value of the peak intensity I ₁ of the (322) plane attributable to the cubic structure of the protonic heteropolyacid to the value of from 0.01 to 0.80.

Description

METHOD FOR MANUFACTURING METHACRYLIC ACID AND METHOD FOR MANUFACTURING THE SAME,

The present invention relates to a catalyst for the production of methacrylic acid, a process for producing the same, and a process for producing methacrylic acid and methacrylic acid ester.

Heteropoly acid catalysts including molybdenum element and phosphorus element are known as catalysts for the production of methacrylic acid used in the production of methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen. Examples of such a heteropoly acid catalyst include a proton type heteropolyacid having a counter cation as a proton and a heteropoly acid salt in which a part of the proton is replaced with a cation other than a proton. As the heteropoly acid salt, an alkali metal salt in which the cation is an alkali metal ion and an ammonium salt in which the cation is an ammonium ion are known. On the other hand, the proton-type heteropolyacid is water-soluble, but the alkali metal salt of heteropoly acid is generally poorly soluble because the ionic radius of the cation is large (Non-Patent Document 1).

Patent Literature 1 discloses a method for producing a polylactic acid which comprises an acidic salt of ketene type heteropoly acid including phosphorus and molybdenum and has a peak intensity ratio of 3.24 to 3.26 ANGSTROM to a peak intensity to peak intensity of 3.38 to 3.41 ANGSTROM in X- 0.001 to 0.01. ≪ / RTI >

Japanese Patent Application Laid-Open No. 2005-131577

 Masayuki Otake, Takeshi Onoda, Catalyst, vol. 18, No. 6 (1976)

However, in the case of using the catalyst described in Patent Document 1 in the production of methacrylic acid by gas-phase catalytic oxidation of methacrolein with molecular oxygen, the yield of methacrylic acid as an industrial catalyst is not sufficient, and further improvement is desired . An object of the present invention is to provide a catalyst for the production of methacrylic acid having a high yield of methacrylic acid.

The present invention is the following [1] to [11].

[1] A catalyst for the production of methacrylic acid, which comprises at least phosphorus, a molybdenum and a vanadium-containing heteropoly acid salt, which is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, (222) plane attributable to the cubic structure of the heteropoly acid in the X-ray diffraction pattern using the Cu-K? Line of the catalyst for the production of methacrylic acid, which was allowed to stand for 12 hours under an environment maintained at 30 占 폚 and a humidity of 90% for an absolute value of _0, the ratio (I ₁ / I ₀₎ of the absolute value of the (322) peak intensity I ₁ of the surface due to the cubic structure of the proton type heteropoly acid is, 0.01 or more 0.80 or less, a methacrylic acid-producing catalyst.

[2] The catalyst for the production of methacrylic acid according to [1], wherein I ₁ / I ₀ is 0.05 or more and 0.75 or less.

[3] The catalyst for the production of methacrylic acid according to [2], wherein I ₁ / I ₀ is 0.40 or more and 0.73 or less.

[4] A process for producing a catalyst for the production of methacrylic acid according to any one of [1] to [3], comprising a step of mixing a heteropoly acid salt-containing liquid i comprising at least a phosphorus raw material and an alkali metal ion raw material, A process for producing a catalyst for producing methacrylic acid, comprising a step of obtaining a catalyst precursor by drying using a heteropoly acid salt-containing liquid ii containing a raw material.

[5] The method for producing a catalyst for producing methacrylic acid according to [4], which comprises a step of mixing a dried product of the heteropoly acid salt-containing liquid i and a dried product of the heteropoly acid salt-containing liquid ii to obtain a catalyst precursor.

[6] The catalyst for the production of methacrylic acid according to [4], which comprises a step of mixing the heteropoly acid salt-containing liquid i and the heteropoly acid salt-containing liquid ii to obtain a heteropoly acid salt-containing liquid iii and drying it to obtain a catalyst precursor Gt;

[7] A process for producing a heteropoly acid salt-containing liquid iv by mixing a solution of the heteropoly acid salt-containing liquid i and the solution of the heteropoly acid salt-containing liquid ii in one of the other heteropoly acid salt-containing liquids to obtain a catalyst precursor [4] The method for producing a catalyst for producing methacrylic acid according to [4].

[8] The process for producing a catalyst for producing methacrylic acid according to any one of [4] to [7], wherein the heteropoly acid salt-containing liquids i and ii satisfy the following formulas (1) to (3).

   1.5? AMi / Pi? 3.0 (1)

4.0? NH ₄ ii / Pii? 5.0 (2)

   1.0? Pii / Pi? 2.0 (3)

A (wherein 1 to 3 of, AMi is the number of moles of alkali metal ions contained in the heteropolyacid-containing liquid i, Pi is a liquid containing phosphorus molar amount, NH ₄ ii is the heteropolyacid contained in the heteropolyacid-containing liquid i ii The number of moles of ammonium ions contained, and Pii the number of moles of phosphorus contained in the heteropoly acid-containing liquid ii.

[9] A process for producing methacrylic acid, wherein methacrylic acid is produced by gas-phase catalytic oxidation of methacrolein with molecular oxygen in the presence of the catalyst for the production of methacrylic acid according to any one of [1] to [3].

[10] A method for producing methacrylic acid ester by esterifying methacrylic acid produced by the methacrylic acid production method described in [9].

[11] A method for producing methacrylic acid by producing methacrylic acid by the method described in [9] and esterifying the methacrylic acid.

According to the present invention, a catalyst for producing methacrylic acid having a high yield of methacrylic acid can be provided.

[Catalyst for the Production of Methacrylic Acid]

The catalyst for the production of methacrylic acid according to the present invention comprises a heteropoly acid salt containing at least phosphorus, molybdenum and vanadium, which is used in producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, Catalyst. The catalyst was subjected to X-ray diffraction (XRD) using a Cu-K? Line of a catalyst (hereinafter also referred to as a catalyst after pretreatment) in which the catalyst was allowed to stand for 12 hours under an environment maintained at a temperature of 30 ° C. and a humidity of 90% The ratio of the absolute value of the peak intensity I ₁ of the (322) plane due to the cubic structure of the protonic heteropoly acid to the absolute value of the peak intensity I ₀ of the (222) plane attributable to the cubic structure of the heteropoly acid salt I ₁ / I ₀ ) (hereinafter, also referred to as peak intensity ratio (I ₁ / I ₀ )) is not less than 0.01 and not more than 0.80.

The elemental composition of the catalyst for the production of methacrylic acid according to the present invention is not particularly limited as long as it contains at least phosphorus, molybdenum and vanadium, but may further contain other elements in addition to phosphorus, molybdenum and vanadium. Examples of other elements include copper, cesium and the like. These may further include one species or two or more species. In particular, the catalyst for the production of methacrylic acid according to the present invention preferably has an elemental composition represented by the following formula (4) in view of the yield of methacrylic acid.

Mo _a P _b V _c Cu _{d e} E _f G _g O _h (4)

In the formula (4), Mo, P, V, Cu and O are each an atomic symbol representing molybdenum, phosphorus, vanadium, copper and oxygen. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten and boron. E is a group consisting of iron, zinc, chromium, magnesium, calcium, strontium, tantalum, cobalt, nickel, manganese, barium, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, cerium and lanthanum ≪ / RTI > G represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium. b = 0.5 to 3, c = 0.01 to 3, d = 0.01 to 2, and e = 1 to 12, wherein a, b, c, d, e, f, g and h represent atomic ratios of the respective elements. 0.1 to 3, f = 0 to 3, g = 0.01 to 3, and h is the atomic ratio of oxygen required to satisfy the valence of each element. On the other hand, the element composition is a value calculated by analyzing a component in which the catalyst is dissolved in ammonia water by ICP emission spectrometry.

In the present invention, when the X-ray diffraction pattern of the catalyst according to the present invention is subjected to the pretreatment after the pretreatment and the X-ray diffraction pattern using the Cu-K? Ray is measured, the peak intensity ratio (I ₁ / I ₀ ) Or more and 0.80 or less. When the peak intensity ratio (I ₁ / I ₀ ) is 0.01 or more, the adsorption sites of methacrolein on the surface of the catalyst are increased and the catalytic activity is improved. Further, when the peak intensity ratio (I ₁ / I ₀ ) is 0.80 or less, progress of the sequential oxidation of methacrylic acid can be suppressed. Therefore, when the catalyst according to the present invention is used for the production of methacrylic acid, methacrylic acid is obtained in a high yield. In addition, by having the heteropoly acid salt and the protonic heteropoly acid at a predetermined ratio as in the present invention, it is expected that a high methacrylic acid yield can be maintained even when the catalyst is used for a long period of time.

In the measurement of the X-ray diffraction pattern, the catalyst for producing methacrylic acid is first pretreated. The pretreatment is carried out by allowing the catalyst to stand under an environment maintained at a humidity of 90% for 12 hours at a temperature of 30 占 폚. By carrying out the pretreatment, the water molecules are hydrated in the heteropoly acid contained in the catalyst for methacrylic acid production to form a cubic structure of the protonic heteropoly acid. The pre-treated catalyst subjected to the pretreatment was subjected to X-ray diffraction (large negative Cu-K? Line) to obtain a diffraction pattern. The absolute value of the peak intensity I ₀ of the (222) plane attributed to the cubic structure of the heteropoly acid salt, (I ₁ / I ₀ ) of the absolute value of the peak intensity I ₁ of the (322) plane attributed to the cubic structure of the heteropolyacid type heteropolyacid is calculated.

For example, in the case of Cs ₄ PVMo ₁₁ O ₄₀ , which is a heteropoly acid salt containing cesium as a cation, the peak of the (222) plane appears at a position of 2? = 26.241 ° (Troemel, M., Inst. Frankfurt, Germany, ICDD Grant-in-Aid (1995)). Further, in the case of H ₄ PVMo ₁₁ O ₄₀ .32H ₂ O, which is a protonic heteropoly acid, the peak of the (322) plane appears at 2θ = 26.801 ° (Troemel, M., Inst. , ICDD Grant-in-Aid (1994)). In addition, the positions of the peaks do not always coincide with each other due to the difference in the number of polyatomic and heteroatom-containing heteroatomic elements and the number of equivalents of cations of the heteropolyacid salt. However, the position of the surface can be confirmed by looking at the peak pattern. When a plurality of salts exist as the heteropoly acid salt and a plurality of peak patterns can be identified, the sum of the absolute values of the intensities of the respective peaks of the (222) plane caused by the cubic structure of the heteropoly acid salt is I ₀ . The same is true for I ₁ . The X-ray diffraction pattern can be measured with an X-ray structure analyzer (trade name: X'Pert PRO MPD, manufactured by PANalytical).

The peak intensity ratio (I ₁ / I ₀₎ is not less than 0.01 less than 0.80, the higher meth In view to achieve the methacrylic acid yield, and the lower limit or more is preferable, more than 0.40 preferably more than 0.05, more than 0.50 More preferable. The upper limit is preferably 0.75 or less, more preferably 0.73 or less, still more preferably 0.70 or less.

[Production method of catalyst for methacrylic acid production]

The method for producing the catalyst for the production of methacrylic acid according to the present invention is not particularly limited, but can be produced, for example, by the following method. The method includes a step of dissolving or suspending at least a phosphorus raw material, a molybdenum raw material and a vanadium raw material in a solvent to prepare a catalyst raw material liquid (hereinafter also referred to as a catalyst raw material liquid preparing step), and a step of adding a cation raw material (Hereinafter also referred to as a step of adding a cation), a step of drying the heteropoly acid salt-containing liquid to obtain a catalyst precursor (hereinafter also referred to as a drying step), a step of adding the catalyst precursor And a step of producing a catalyst for producing methacrylic acid by heat treatment (hereinafter also referred to as a heat treatment step). Here, the step of forming the catalyst precursor before the heat treatment step (hereinafter also referred to as a molding step) may be included. Particularly, the process for producing a catalyst for the production of methacrylic acid according to the present invention is characterized in that a heteropoly acid salt containing liquid i containing at least a phosphorus raw material and an alkali metal ion raw material and a heteropoly acid salt containing liquid ii containing at least a phosphorus raw material and an ammonium ion raw material are used And a step of obtaining a catalyst precursor by drying.

(Catalyst raw material liquid preparation step)

In this step, at least a phosphorus raw material, a molybdenum raw material, and a vanadium raw material are dissolved or suspended in a solvent to prepare a catalyst raw material liquid.

The raw material compound of each element is not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halides, oxo acids and oxoates of the respective elements may be used alone or in combination of two or more. For example, as the phosphorus raw material, phosphoric acid, phosphorus pentoxide, ammonium phosphate and the like can be used. As the molybdenum raw material, molybdenum trioxide, ammonium paramolybdodecanoate, molybdenum acid, molybdenum chloride and the like can be used. As the vanadium raw material, ammonium metavanadate, in vanadium molybdenum acid, vanadium pentoxide and the like can be used. These may be used alone or in combination of two or more.

As the solvent for dissolving or suspending the raw material, water, ethyl alcohol, acetone and the like can be used. These may be used alone or in combination of two or more. Among them, water is preferable as a solvent.

On the other hand, in the present step, one kind of catalyst raw material liquid may be prepared, or two or more kinds may be prepared. Particularly, it is preferable to prepare two or more catalyst raw material liquids and mix them before and after the drying step described later from the viewpoint of easily controlling the peak intensity ratio (I ₁ / I ₀ ) within the range of the present invention.

(Cation addition process)

In this step, a cationic raw material is added to the catalyst raw material liquid obtained by the above-described process for preparing a raw material liquid to obtain a heteropoly acid salt-containing liquid.

Here, the cation is capable of forming a heteropoly acid salt having a cubic crystal structure, and is preferably an alkali metal ion such as potassium, rubidium, cesium and the like, and an ammonium ion. When the cation is an alkali metal ion, examples of the cationic raw material include a carbonate, a hydrogencarbonate, a hydroxide, a chloride salt, a sulfate, and a nitrate of an alkali metal. When the cation is an ammonium ion, examples of the cationic raw material include ammonium hydrogencarbonate, ammonium carbonate, ammonium nitrate, ammonia water and the like. These may be used alone or in combination of two or more. On the other hand, in the process of preparing the catalyst raw material liquid, cations may be contained in the catalyst raw material liquid by using an alkali metal salt or an ammonium salt of each element as a raw material of each element. As the cation raw material, it is preferable to use both the alkali metal ion raw material and the ammonium ion raw material from the viewpoint of the yield of methacrylic acid.

When the cation raw material is added to the catalyst raw material liquid, it is preferable to add the catalyst raw material liquid while stirring. The temperature for adding the cationic raw material is preferably 1 to 100 占 폚. After the addition of all or a part of the cationic raw material, the mixture is preferably heated and stirred at 90 to 150 캜 for 1 to 10 hours.

By changing the amount of the cation raw material to be added in the present step, the peak intensity ratio (I ₁ / I ₀ ) can be adjusted to 0.01 or more and 0.80 or less. When two or more kinds of catalyst raw material liquids are prepared in the above-described process for preparing a raw material liquid for catalyst, a heteropoly acid salt-containing liquid can be prepared by adding a cationic raw material to at least one kind of catalyst raw material liquid in this step. In particular, the heteropoly acid salt-containing liquid i and, to prepare a heteropoly acid salt-containing liquid ii comprises at least the raw materials and the ammonium ion material, the peak intensity ratio (I ₁ / I _0, which includes at least a raw material and an alkali metal ion material From the viewpoint of easy control. It is more preferable that the heteropoly acid salt-containing liquids i and ii satisfy the following formulas (1) to (3) from the viewpoint of easily controlling the peak intensity ratio (I ₁ / I ₀ ).

   1.5? AMi / Pi? 3.0 (1)

4.0? NH ₄ ii / Pii? 5.0 (2)

   1.0? Pii / Pi? 2.0 (3)

Equation (1) to (3) of, AMi is the number of moles of alkali metal ions contained in the heteropolyacid-containing liquid i, Pi is the number of moles of the element, NH ₄ ii is the heteropoly acid-containing liquid contained in the liquid i containing the heteropoly ii And Pii represents the number of moles of phosphorus contained in the heteropoly acid-containing liquid ii. In the above formula (1), AMi / Pi represents the ratio of the number of moles of the alkali metal ion to the phosphorus element in the heteropoly acid-containing liquid i. The lower limit of AMi / Pi is preferably 1.7 or more and the upper limit is preferably 2.8 or less, more preferably 1.9 or more, and the upper limit is 2.6 or less. In the formula (2), NH ₄ ii / Pii represents the ratio of the number of moles of ammonium ions to the phosphorus element in the heteropoly acid-containing liquid ii. The lower limit of NH ₄ ii / Pii is preferably at least 4.1 and the upper limit is preferably at most 4.9, and the lower limit is more preferably at least 4.2 and the upper limit is preferably at most 4.8. In the formula (3), Pii / Pi represents the mixing ratio of the heteropoly acid-containing liquids i and ii. The lower limit of Pii / Pi is preferably 1.1 or more and the upper limit is preferably 1.9 or less, more preferably 1.2 or less and the upper limit is 1.8 or less.

As a method for adjusting the peak intensity ratio (I ₁ / I ₀ ), for example, a method of adjusting the value of Pii / Pi within the range in which the heteropoly acid salt-containing liquids i and ii satisfy the above formulas (1) . The peak intensity ratio (I ₁ / I ₀ ) increases when Pii / Pi is increased, and the peak intensity ratio (I ₁ / I ₀ ) decreases when Pii / Pi is decreased.

(Drying step)

In this step, the heteropoly acid salt-containing liquid obtained by the cation addition step is dried to obtain a catalyst precursor.

The conditions such as the drying method and the drying temperature are not particularly limited and can be appropriately selected depending on the shape and size of the desired dried material. Examples of the drying method include a drying method using a box-type dryer, a drum drying method, an air flow drying method, a vapor drying method, and a spray drying method. The drying temperature may be, for example, 120 to 500 DEG C, and the lower limit is preferably 140 DEG C or more and the upper limit is preferably 400 DEG C or less. The drying can be carried out until the heteropoly acid salt-containing liquid is dried.

The structure of the obtained catalyst precursor can be confirmed by measuring by infrared absorption analysis. Preferably, the catalyst precursor has a keel type heteropoly acid structure. When the catalyst precursor has a keel type heteropoly acid structure, the obtained infrared absorption spectrum has a characteristic peak near 1060, 960, 870, 780 cm ^-1 .

On the other hand, when there are two or more heteropoly acid salt-containing liquids obtained in the cation addition step, they can be mixed before and after the present step. That is, the mixing may be carried out in the liquid containing the heteropoly acid salt before drying, or in the state of the catalyst precursor after drying. Further, after the liquid containing at least one heteropoly acid salt is dried, it may be mixed again with another heteropoly acid salt-containing liquid and dried again to obtain a catalyst precursor. Controlling the peak intensity ratio (I ₁ / I ₀ ) in the resulting catalyst by mixing two or more kinds of heteropoly acid salt-containing liquids containing a heteropoly acid salt having different atomic ratios or a catalyst precursor within the range of the present invention, Is preferable in view of the yield of methacrylic acid. In particular, by mixing two or more kinds of catalyst precursors including heteropoly acid salts having different atomic ratios, a catalyst having a higher yield of methacrylic acid can be obtained.

When the heteropoly acid salt-containing liquids i and ii are used, the catalyst precursor can be obtained by the above drying. For example, a catalyst precursor can be obtained by mixing the dried product of the heteropoly acid salt-containing liquid i and the dried product of the heteropoly acid salt-containing liquid ii. Further, the heteropoly acid salt-containing liquid i and the heteropoly acid salt-containing liquid ii are mixed to obtain a heteropoly acid salt-containing liquid iii, which is then dried to obtain a catalyst precursor. In addition, a dried product of the heteropoly acid salt-containing liquid i and the heteropoly acid salt-containing liquid ii is mixed with the other heteropoly acid salt-containing liquid to obtain a heteropoly acid salt-containing liquid iv, which is then dried to obtain a catalyst precursor.

(Molding step)

The catalyst precursor obtained by the drying step may be formed before the heat treatment step described later. The molding method is not particularly limited, and a known dry or wet molding method can be applied. For example, tablet molding, press molding, extrusion molding, and granulation molding. The shape of the molded article is not particularly limited, and examples thereof include a cylindrical shape, a ring shape, and a spherical shape. In molding, it is preferable to form only the catalyst precursor without adding a carrier or a binder to the catalyst precursor. However, if necessary, known additives such as graphite and talc, a known binder derived from an organic material and an inorganic material, May be added.

(Heat treatment process)

In this step, a catalyst precursor obtained by the above-mentioned drying step or a formed product of a catalyst precursor obtained by the above-mentioned molding step (hereinafter referred to as a medium catalytic precursor) is heat-treated to prepare a catalyst for methacrylic acid production. For example, the catalyst precursor can be heat-treated under the flow of at least one of air and an inert gas. Herein, the inert gas means a gas which does not lower the catalytic activity, and examples thereof include nitrogen, carbon dioxide gas, helium, argon and the like. These may be used alone or in combination of two or more. The heat treatment is preferably carried out under the flow of an oxygen-containing gas such as air.

The shape of the heat treatment vessel is not particularly limited, but it is preferable to use a tubular heat treatment vessel having a sectional area of 2 to 100 cm 2. The heat treatment temperature is preferably not less than 300 ° C and not more than 700 ° C, more preferably not less than 320 ° C and not more than 450 ° C.

The structure of the obtained catalyst for methacrylic acid production can be confirmed by measuring by infrared absorption analysis. The catalyst for producing methacrylic acid preferably has a ketal type heteropoly acid structure. When the catalyst for producing methacrylic acid has a ketal type heteropoly acid structure, the obtained infrared absorption spectrum has a characteristic peak near 1060, 960, 870 and 780 cm ^-1 .

[Method for producing methacrylic acid]

The method for producing methacrylic acid according to the present invention is a method for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen in the presence of the catalyst for the production of methacrylic acid according to the present invention. According to this method, methacrylic acid can be produced at a high yield and the yield of high methacrylic acid can be maintained for a long time.

More specifically, methacrylic acid can be produced by bringing a raw material gas containing methacrolein and molecular oxygen into contact with the catalyst for the production of methacrylic acid according to the present invention. This reaction can be carried out in a fixed phase. The catalyst layer may be a single layer or two or more layers. The catalyst for producing methacrylic acid may contain other additives. The concentration of methacrolein in the raw material gas is not particularly limited, but is preferably 1 to 20% by volume, more preferably 3% by volume or more, and more preferably 10% by volume or less. The methacrolein may contain a small amount of an impurity such as a lower saturated aldehyde that does not substantially affect the present reaction. The concentration of molecular oxygen in the raw material gas is preferably 0.4 to 4.0 moles with respect to 1.0 moles of methacrolein, more preferably 0.5 mole or more, and most preferably 3.0 mole or less. On the other hand, as a molecular oxygen source, air is preferable from the viewpoint of economical efficiency. If necessary, a gas obtained by enriching molecular oxygen by adding pure oxygen to air may be used.

The raw material gas may be one obtained by diluting methacrolein and molecular oxygen with an inert gas such as nitrogen or carbon dioxide gas. In addition, steam may be added to the raw material gas. By conducting the reaction in the presence of water vapor, methacrylic acid can be obtained at a higher selectivity. The concentration of water vapor in the raw material gas is preferably 0.1 to 50.0% by volume, more preferably 1.0% by volume or more, and more preferably 40.0% by volume or less. The contact time of the raw material gas with the catalyst for producing methacrylic acid is preferably 1.5 to 15.0 seconds, more preferably 2.0 seconds or more, and 5.0 seconds or less. The reaction pressure is preferably 0.1 MPa (G) to 1.0 MPa (G). On the other hand, (G) means a gauge pressure. The reaction temperature is preferably 200 to 450 占 폚, more preferably 250 占 폚 or higher and the upper limit is 400 占 폚 or lower.

[Method for producing methacrylic acid ester]

The process for the preparation of methacrylic acid esters according to the present invention esterifies the methacrylic acid produced by the process according to the invention. According to this method, a methacrylic acid ester can be obtained by using methacrylic acid obtained by gas phase catalytic oxidation of methacrolein. The alcohol to be reacted with methacrylic acid is not particularly limited, and examples thereof include methanol, ethanol, isopropanol, n-butanol and isobutanol. As the methacrylic acid ester to be obtained, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and the like can be given. The reaction can be carried out in the presence of an acidic catalyst such as a sulfonic acid type cation exchange resin. The reaction temperature is preferably 50 to 200 占 폚.

Example

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In the Examples and Comparative Examples means " part (s) by mass ". The X-ray diffraction pattern was measured with an X-ray structure analyzer (trade name: X'Pert PRO MPD, manufactured by PANalytical). The analysis of the raw material gas and the product was carried out by gas chromatography. From the results of the gas chromatography, the conversion of methacrolein, the selectivity of methacrylic acid to be produced, and the yield of methacrylic acid were determined by the following formulas.

  Methacrolein conversion rate (%) = (? /?) × 100

  Methacrylic acid selectivity (%) = (? /?) X 100

  (%) Of methacrylic acid = (? /?) × 100

In the formula,? Represents the number of carbon atoms in the supplied methacrolein,? Represents the number of carbon atoms in the methacrolein reacted, and? Represents the number of carbon atoms in the produced methacrylic acid.

[Example 1]

33 parts of molybdenum trioxide, 2.5 parts of ammonium metavanadate, 2.2 parts of an 85 mass% aqueous phosphoric acid solution and 2.3 parts of copper (II) nitrate trihydrate were dissolved in 132 parts of pure water. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 캜, 8.6 parts of cesium bicarbonate dissolved in 20 parts of pure water was added with stirring using a rotary blade stirrer and stirred for 15 minutes to precipitate a cesium salt of heteropoly acid. The resulting heteropoly acid salt-containing liquid i-1 was evaporated to dryness to obtain a catalyst precursor A1. On the other hand, in 216 parts of pure water, 54 parts of molybdenum trioxide, 4.1 parts of ammonium metavanadate, 3.6 parts of an 85% by mass aqueous phosphoric acid solution and 3.8 parts of copper (II) nitrate trihydrate were dissolved. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 캜, 4.8 parts of ammonium carbonate dissolved in 20 parts of pure water was added with stirring using a rotary blade stirrer and stirred for 15 minutes to precipitate the ammonium salt of heteropoly acid. The resulting heteropoly acid salt-containing liquid ii-1 was evaporated to dryness to obtain a catalyst precursor B1. Next, the catalyst precursors A1 and B1 were mixed to obtain a catalyst precursor.

The obtained catalyst precursor was molded, and a molded product was placed in a cylindrical quartz glass firing container having an inner diameter of 3 cm. The temperature was raised to 10 ° C / h under air circulation, and the mixture was calcined at 380 ° C for 5 hours to prepare a catalyst for methacrylic acid production. The catalyst for the production of methacrylic acid had a ketal type heteropoly acid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.9 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. Further, when the catalyst was allowed to stand for 12 hours in an environment maintained at a temperature of 30 ° C and a humidity of 90%, the catalyst after the pretreatment was measured for an X-ray diffraction pattern using a Cu-Kα line. As a result, I ₀ was 2θ = 26.1 ° and I ₁ were found at 2θ = 26.3 °, and the peak intensity ratio I ₁ / I ₀ was 0.43.

The obtained methacrylic acid-producing catalyst was charged in a reaction tube and reacted at a reaction temperature of 300 占 폚 through a feed gas comprising 5% by volume of methacrolein, 10% by volume of oxygen, 30% by volume of steam and 55% by volume of nitrogen. The product was collected and analyzed by gas chromatography to calculate the yield of methacrylic acid and the like. The results are shown in Table 1.

[Example 2]

Catalyst precursor A1 was obtained in the same manner as in Example 1. [ On the other hand, in 240 parts of pure water, 60 parts of molybdenum trioxide, 4.6 parts of ammonium metavanadate, 4.0 parts of an 85% by mass aqueous phosphoric acid solution and 4.2 parts of copper (II) nitrate trihydrate were dissolved. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 캜, 5.3 parts of ammonium carbonate dissolved in 22.2 parts of pure water was added with stirring using a rotary blade stirrer and stirred for 15 minutes to precipitate the ammonium salt of heteropoly acid. The resulting heteropoly acid salt-containing liquid ii-2 was evaporated to dryness to obtain a catalyst precursor B2. Next, the catalyst precursors A1 and B2 were mixed to obtain a catalyst precursor.

Thereafter, a catalyst for producing methacrylic acid was prepared from the catalyst precursor by the same method as in Example 1, and methacrylic acid was produced using the catalyst. The catalyst for the production of methacrylic acid had a ketal type heteropoly acid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.8 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. The catalyst after the pretreatment was prepared in the same manner as in Example 1, and the X-ray diffraction pattern of the catalyst after the pretreatment using the Cu-K? Ray was measured. As a result, I ₀ was 2? = 26.1 ° and I ₁ was 2? °, and the peak intensity ratio I ₁ / I ₀ was 0.69. The results are shown in Table 1.

[Example 3]

50 parts of molybdenum trioxide, 3.8 parts of ammonium metavanadate, 3.3 parts of an 85% by mass aqueous phosphoric acid solution and 3.5 parts of copper (II) nitrate trihydrate were dissolved in 200 parts of pure water. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 캜, 13.0 parts of cesium bicarbonate dissolved in 20 parts of pure water was added with stirring using a rotating blade stirrer and stirred for 15 minutes to precipitate a cesium salt of heteropoly acid to obtain a heteropoly acid salt-containing liquid i-2 . On the other hand, in 280 parts of pure water, 70 parts of molybdenum trioxide, 5.3 parts of ammonium metavanadate, 4.7 parts of an 85% by mass aqueous phosphoric acid solution and 4.9 parts of copper (II) nitrate trihydrate were dissolved. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 占 폚, 6.8 parts of ammonium carbonate dissolved in 20 parts of pure water was added with stirring using a rotary blade stirrer and stirred for 15 minutes to precipitate the ammonium salt of heteropoly acid to obtain heteropoly acid salt-containing liquid ii-3 . The heteropoly acid salt-containing liquids i-2 and ii-3 were mixed, and the resulting heteropoly acid salt-containing liquid iii-1 was stirred for 15 minutes while being maintained at 95 캜, followed by evaporating and drying to obtain a catalyst precursor.

Thereafter, a catalyst for producing methacrylic acid was prepared from the catalyst precursor by the same method as in Example 1, and methacrylic acid was produced using the catalyst. The catalyst for the production of methacrylic acid had a ketal type heteropoly acid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _1.0 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. The catalyst after the pretreatment was prepared in the same manner as in Example 1, and the X-ray diffraction pattern of the catalyst after the pretreatment using the Cu-K? Ray was measured. As a result, I ₀ was 2? = 26.2 占 and I ₁ was 2? °, and the peak intensity ratio I ₁ / I ₀ was 0.09. The results are shown in Table 1.

[Example 4]

25 parts of molybdenum trioxide, 1.9 parts of ammonium metavanadate, 1.7 parts of an 85% by mass aqueous phosphoric acid solution and 1.8 parts of copper (II) nitrate trihydrate were dissolved in 100 parts of pure water. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 占 폚, 6.5 parts of cesium bicarbonate dissolved in 10 parts of pure water was added with stirring using a rotary blade stirrer and stirred for 15 minutes to precipitate a cesium salt of heteropoly acid. The resulting heteropoly acid salt-containing liquid i-3 was evaporated to dryness to obtain a catalyst precursor A2. On the other hand, 75 parts of molybdenum trioxide, 5.6 parts of ammonium metavanadate, 5.0 parts of an 85% by mass aqueous phosphoric acid solution, and 5.3 parts of copper (II) nitrate trihydrate were dissolved in 300 parts of pure water. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. The resulting heteropoly acid salt-containing liquid ii-4 was evaporated to dryness to obtain a catalyst precursor B3. Next, the catalyst precursors A2 and B3 were mixed to obtain a catalyst precursor.

Thereafter, a catalyst for producing methacrylic acid was prepared from the catalyst precursor by the same method as in Example 1, and methacrylic acid was produced using the catalyst. The catalyst for the production of methacrylic acid had a ketal type heteropoly acid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.6 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. The catalyst after the pretreatment was prepared in the same manner as in Example 1, and the X-ray diffraction pattern of the catalyst after the pretreatment using the Cu-K? Ray was measured. As a result, I ₀ was 2? = 26.1 ° and I ₁ was 2? °, and the peak intensity ratio I ₁ / I ₀ was 0.75. The results are shown in Table 1.

[Comparative Example 1]

100 parts of molybdenum trioxide, 7.5 parts of ammonium metavanadate, 6.7 parts of an 85% by mass aqueous phosphoric acid solution, and 7.0 parts of copper (II) nitrate trihydrate were dissolved in 400 parts of pure water. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 占 폚, 26.0 parts of cesium bicarbonate dissolved in 40 parts of pure water was added with stirring using a rotary blade stirrer and stirred for 15 minutes to precipitate a cesium salt of heteropoly acid. The resulting heteropoly acid salt-containing liquid i-4 was evaporated to dryness to obtain a catalyst precursor.

Thereafter, a catalyst for producing methacrylic acid was prepared from the catalyst precursor by the same method as in Example 1, and methacrylic acid was produced using the catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _2.3 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. The catalyst after the pretreatment was prepared in the same manner as in Example 1, and the X-ray diffraction pattern of the catalyst after the pretreatment using the Cu-K? Ray was measured. As a result, I ₀ was found at 2θ = 26.0 °. On the other hand, since I ₁ could not be confirmed, it was set to zero. Therefore, the peak intensity ratio I ₁ / I ₀ was 0.00. The results are shown in Table 1.

[Comparative Example 2]

Catalyst precursor A1 was obtained in the same manner as in Example 1. [ On the other hand, in 280 parts of pure water, 70 parts of molybdenum trioxide, 5.3 parts of ammonium metavanadate, 4.7 parts of an 85% by mass aqueous phosphoric acid solution and 4.9 parts of copper (II) nitrate trihydrate were dissolved. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 占 폚, 6.2 parts of ammonium carbonate dissolved in 25.9 parts of pure water was added with stirring using a rotary blade stirrer and stirred for 15 minutes to precipitate an ammonium salt of heteropoly acid. The resulting heteropoly acid salt-containing liquid ii-5 was evaporated to dryness to obtain a catalyst precursor B4. Next, the catalyst precursors A1 and B4 were mixed to obtain a catalyst precursor.

Thereafter, a catalyst for producing methacrylic acid was prepared from the catalyst precursor by the same method as in Example 1, and methacrylic acid was produced using the catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.7 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. The catalyst after the pretreatment was prepared in the same manner as in Example 1, and the X-ray diffraction pattern of the catalyst after the pretreatment using the Cu-K? Ray was measured. As a result, I ₀ was 2? = 26.1 ° and I ₁ was 2? °, and the peak intensity ratio I ₁ / I ₀ was 0.81. The results are shown in Table 1.

[Comparative Example 3]

Catalyst precursor A1 was obtained in the same manner as in Example 1. [ On the other hand, 1145 parts of molybdenum trioxide, 8.6 parts of ammonium metavanadate, 7.6 parts of an 85% by mass aqueous phosphoric acid solution and 8.0 parts of copper (II) nitrate trihydrate were dissolved in 455.2 parts of pure water. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. The solution temperature was maintained at 95 캜, and 10.1 parts of ammonium carbonate dissolved in 42.1 parts of pure water was added while stirring with a rotary blade stirrer, followed by stirring for 15 minutes to precipitate an ammonium salt of heteropoly acid. The resulting heteropoly acid salt-containing liquid ii-6 was evaporated to dryness to obtain a catalyst precursor B5. Next, the catalyst precursors A1 and B5 were mixed to obtain a catalyst precursor.

Thereafter, a catalyst for producing methacrylic acid was prepared from the catalyst precursor by the same method as in Example 1, and methacrylic acid was produced using the catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.5 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. The catalyst after the pretreatment was prepared in the same manner as in Example 1, and the X-ray diffraction pattern of the catalyst after the pretreatment using Cu-K? Ray was measured. As a result, I ₀ was 2? = 26.2 占 and I ₁ was 2? = 26.4 °, and the peak intensity ratio I ₁ / I ₀ was 2.25. The results are shown in Table 1.

[Comparative Example 4]

100 parts of molybdenum trioxide, 7.5 parts of ammonium metavanadate, 6.7 parts of an 85% by mass aqueous phosphoric acid solution, and 7.0 parts of copper (II) nitrate trihydrate were dissolved in 400 parts of pure water. This was heated to 95 ° C while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. The resulting heteropoly acid salt-containing liquid ii-7 was evaporated to dryness to obtain a catalyst precursor.

Thereafter, a catalyst for producing methacrylic acid was prepared from the catalyst precursor by the same method as in Example 1, and methacrylic acid was produced using the catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 . On the other hand, the composition of the element was calculated by analyzing the component in which the catalyst was dissolved in ammonia water by ICP emission spectrometry. The catalyst after the pretreatment was prepared in the same manner as in Example 1, and the X-ray diffraction pattern of the catalyst after the pretreatment using Cu-K? Ray was measured. As a result, I ₁ was found at 2θ = 26.5 °. On the other hand, I ₀ was set because I ₀ was not observed. Therefore, the peak intensity ratio I ₁ / I ₀ could not be calculated. The results are shown in Table 1.

In Examples 1 to 4, it was confirmed that the peak intensity ratio (I ₁ / I ₀ ) was within the range specified in the present invention and the catalyst had a high methacrylic acid yield. Among them, the highest methacrylic acid yield was obtained in Example 2 in which the peak intensity ratio (I ₁ / I ₀ ) was 0.69, and the optimum range of peak intensity ratio (I ₁ / I ₀ ) I could.

On the other hand, in Comparative Examples 1 to 4, the peak intensity ratio (I ₁ / I ₀ ) was out of the range specified in the present invention, and the yield of methacrylic acid was lower than in Examples 1 to 4. On the other hand, in Comparative Example 4, the peak pattern due to the heteropoly acid salt was not confirmed, and I ₀ was 0, so that the peak intensity ratio (I ₁ / I ₀ ) could not be calculated. Even in such a case, the yield of methacrylic acid was low, and it was confirmed that the yield of methacrylic acid was low when the peak intensity ratio (I ₁ / I ₀ ) was out of the range specified in the present invention. On the other hand, the methacrylic acid obtained in this embodiment is esterified to obtain methacrylic acid ester.

This application claims priority based on Japanese Patent Application No. 2016-179403, filed on September 14, 2016, the entire disclosure of which is hereby incorporated by reference.

Although the present invention has been described with reference to the embodiments and the examples, the present invention is not limited to the embodiments and examples. The structure and details of the present invention can be variously modified by those skilled in the art within the scope of the present invention.

The catalyst for the production of methacrylic acid according to the present invention is industrially useful because it exhibits a high yield of methacrylic acid when it is used in the production of methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen. In addition, by using the crystal structure of the heteropoly acid salt and the proton-type heteropoly acid, it is expected that the proton-type heteropoly acid effectively functions as the active site while maintaining the stability of the heteropoly acid salt, thereby exhibiting a high yield of methacrylic acid for a long period of time.

Claims (11)

A catalyst for the production of methacrylic acid, which comprises at least phosphorus, molybdenum and vanadium-containing heteropoly acid salts, which is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, In the X-ray diffraction pattern using the Cu-K? Line of the catalyst for the production of methacrylic acid which was allowed to stand for 12 hours under an environment where the humidity was kept at 90%, the absolute value of the peak intensity I ₀ of the (222) plane attributed to the cubic structure of the heteropoly acid salt (I ₁ / I ₀ ) of the absolute value of the peak intensity I ₁ of the (322) plane attributable to the cubic structure of the protonic heteropolyacid to the value of from 0.01 to 0.80. The method according to claim 1,
A catalyst for the production of methacrylic acid, wherein I ₁ / I ₀ is 0.05 or more and 0.75 or less. 3. The method of claim 2,
Wherein I ₁ / I ₀ is 0.40 or more and 0.73 or less. A process for producing a catalyst for the production of methacrylic acid according to any one of claims 1 to 3, comprising the steps of: preparing a heteropoly acid salt-containing liquid i comprising at least a phosphorus raw material and an alkali metal ion raw material; Containing solution ii containing a heteropoly acid salt to obtain a catalyst precursor by drying. 5. The method of claim 4,
And a step of mixing the dried product of the heteropoly acid salt-containing liquid i and the dried product of the heteropoly acid salt-containing liquid ii to obtain a catalyst precursor. 5. The method of claim 4,
A step of mixing the heteropoly acid salt-containing liquid i and the heteropoly acid salt-containing liquid ii to obtain a heteropoly acid salt-containing liquid iii, and drying the solution to obtain a catalyst precursor. 5. The method of claim 4,
Mixing a solution of the heteropoly acid salt-containing liquid i and the solution of the heteropoly acid salt-containing liquid ii in one of the other heteropoly acid salt-containing liquid to obtain a heteropoly acid salt-containing liquid iv and drying it to obtain a catalyst precursor; A process for producing a catalyst for the production of methacrylic acid. 8. The method according to any one of claims 4 to 7,
Wherein the heteropoly acid salt-containing liquids i and ii satisfy the following formulas (1) to (3).
1.5? AMi / Pi? 3.0 (1)
4.0? NH ₄ ii / Pii? 5.0 (2)
1.0? Pii / Pi? 2.0 (3)
A (wherein 1 to 3 of, AMi is the number of moles of alkali metal ions contained in the heteropolyacid-containing liquid i, Pi is a liquid containing phosphorus molar amount, NH ₄ ii is the heteropolyacid contained in the heteropolyacid-containing liquid i ii The number of moles of ammonium ions contained, and Pii the number of moles of phosphorus contained in the heteropoly acid-containing liquid ii. A process for producing methacrylic acid, wherein methacrylic acid is produced by gas-phase catalytic oxidation of methacrolein with molecular oxygen in the presence of the catalyst for the production of methacrylic acid according to any one of claims 1 to 3. A process for producing a methacrylic acid ester by esterifying methacrylic acid produced by the process for producing methacrylic acid according to claim 9. A process for producing methacrylic acid by producing methacrylic acid by the method according to claim 9 and for esterifying the methacrylic acid.