KR102573437B1 - Catalyst for producing methacrylic acid, method for producing same, and method for producing methacrylic acid and methacrylic acid ester - Google Patents

Abstract

A Mo-V-based oxide catalyst for producing methacrylic acid with a higher yield than before is provided. A catalyst used when producing methacrylic acid by oxidation of methacrolein, wherein the catalyst comprises a metal oxide containing molybdenum, and the metal oxide satisfies the following conditions (a) and (b) A catalyst for producing methacrylic acid, characterized in that it has a cyclic structure. (a) A cyclic structure satisfying the following formula (I). (Total number of moles of Mo, V and X): (number of moles of O): O = 7:35 (I) (In formula (I), Mo, V and O represent molybdenum, vanadium and oxygen, respectively. X represents at least one element selected from the group consisting of tungsten, iron, copper, bismuth, etc.) (b) 7 metal-oxygen octahedrons (octahedral structures) each share the oxygen of the adjacent vertex, Combined annular structure.

Description

Catalyst for producing methacrylic acid, method for producing same, and method for producing methacrylic acid and methacrylic acid ester

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

Metal oxide catalysts have been put into practical use as oxidation reactions of oxygen-containing organic substances such as hydrocarbons, carbonyl compounds, and alcohols, ammoxidation, oxidative dehydration, hydrogenation of CO and unsaturated compounds, dehydrogenation catalysts, and solid acid/base catalysts (non-patented). Literature 1).

As a metal oxide catalyst, an oxide catalyst containing molybdenum and vanadium (hereinafter also referred to as "Mo-V-based oxide catalyst") is known. Mo-V-based oxide catalysts are industrialized as catalysts used for selective oxidation or ammoxidation of lower alkanes represented by ethane and propane, and catalysts for producing acrylic acid by selectively oxidizing acrolein. Compared to molybdenum-containing heteropolyacid catalysts, Mo-V-based oxide catalysts are expected to have superior catalyst life because they have excellent heat resistance.

Examples of applying the Mo-V oxide catalyst to the selective oxidation of unsaturated aldehydes include the following. When the Mo-V oxide catalyst was applied to the selective oxidation of acrolein and methacrolein, "acrolein conversion rate 100%, acrylic acid selectivity 97%" and "methacrylic acid conversion rate 57%, methacrylic acid selectivity 19%" were shown, respectively ( Non-Patent Document 2). When a Mo-V-based oxide catalyst containing tungsten was applied to the selective oxidation of acrolein and methacrolein, "acrolein conversion rate 95%, acrylic acid selectivity 90%", "methacrylic acid conversion rate 40%, methacrylic acid selectivity 35%", respectively ” was shown (Non-Patent Document 3). In this way, Mo-V oxides are suitable for selective oxidation of acrolein, but are unsuitable for selective oxidation of methacrolein.

Morooka Yoshihiko, 「Catalyst」, 1984, Vol. 26, No. 2, p. 76 Makoto Misono, 「Applied Catalysis」, 1990, Vol. 64, p. 1-30 A. Drocher, D. Ohlig, S. Knoche, N. Gora, M. Heid, N. Menning, T. Petzold, H. Vogel, Topics in Catalysis, 2016, Vol. 59, p. 1518-1532

As described above, while the Mo-V-based oxide catalyst has excellent heat resistance compared to the molybdenum-containing heteropoly acid-based catalyst, the yield of methacrylic acid is insufficient.

An object of the present invention is to provide a molybdenum-containing oxide catalyst for producing methacrylic acid with a higher yield than before, a method for producing the same, a method for producing methacrylic acid using the catalyst, and a method for producing methacrylic acid ester is in providing

In view of the above problems, the present inventors have intensively studied a molybdenum-containing oxide catalyst that can be suitably used for the oxidation of methacrolein. As a result, a catalyst containing a metal oxide containing a specific cyclic structure has been used. , found that methacrylic acid could be produced in a higher yield than before, and completed the present invention.

That is, the present invention is the following [1] to [40] and [1'] to [21'].

[1] A catalyst used when producing methacrylic acid by oxidation of methacrolein, wherein the catalyst includes a metal oxide containing molybdenum, and the metal oxide is under the following conditions (a) and (b) ), characterized in that it has a cyclic structure that satisfies, a catalyst for producing methacrylic acid.

(a) A cyclic structure satisfying the following formula (I).

(Sum of moles of Mo, V and X): (number of moles of O) = 7:35 (I)

(In formula (I), Mo, V and O represent molybdenum, vanadium and oxygen, respectively. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt represents at least one element selected from the group consisting of rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium.)

(b) Cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygen at adjacent vertices.

[2] The catalyst for producing methacrylic acid according to [1], wherein the metal oxide satisfies the following condition (c).

(c) A metal oxide having a composition represented by formula (II) below.

Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)

(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0≤c<0.5, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)

[3] The catalyst for producing methacrylic acid according to [2], wherein 0<c<0.5 in the formula (II).

[4] The catalyst for producing methacrylic acid according to any one of [1] to [3], wherein the metal oxide satisfies the following condition (d).

(d) A metal oxide that satisfies the following formula (III) when the mass of the metal oxide is M1 and the mass of the inactive component contained in the metal oxide is M2.

0≤M2/M1<0.05 (III)

[5] The catalyst for producing methacrylic acid according to any one of [1] to [4], wherein the metal oxide satisfies the following condition (e).

(e) Difference spectrum between the infrared absorption spectrum obtained by FT-IR measurement of the metal oxide and the infrared absorption spectrum obtained by FT-IR measurement after maintaining the metal oxide in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes The metal oxide having absorption peaks at 1557 ± 10 cm ^-1 , 1456 ± 10 cm ^-1 and 1374 ± 10 cm ^-1 .

[6] The catalyst for producing methacrylic acid according to any one of [1] to [5], wherein the metal oxide satisfies the following condition (f).

(f) A metal oxide having a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60 m ² /g.

[7] The catalyst for producing methacrylic acid according to any one of [1] to [6], wherein the metal oxide satisfies the following condition (g).

(g) A metal oxide showing diffraction peaks at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

[8] The catalyst for producing methacrylic acid according to [7], wherein the metal oxide satisfies the following condition (g1).

(g1) A metal oxide showing diffraction peaks only at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

[9] In the condition (g) above, 2θ = 6.6°±0.3°, 7.9°±0.3°, 9.0°±0.3°, 26.4°±0.3°, 26.9°±0.3°, 27.2°±0.3° and the catalyst for producing methacrylic acid described in [7], which exhibits a diffraction peak at 27.4°±0.3°.

[10] In the above condition (g), 2θ = 4.7°±0.3°, 8.3°±0.3°, 25.3°±0.3°, 25.7°±0.3°, 27.0°±0.3°, 27.9°±0.3° and the catalyst for producing methacrylic acid described in [7], which shows a diffraction peak at 28.3°±0.3°.

[11] A method for producing the catalyst for producing methacrylic acid according to any one of [1] to [10],

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;

(2) Step of firing the solid content to obtain a metal oxide

Method for producing a catalyst for producing methacrylic acid comprising a.

[12] As a method for producing the catalyst for producing methacrylic acid according to [9] or [10],

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;

(1b) dispersing the solid content in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid content;

(2b) Step of firing the solid content obtained in (1b) to obtain a metal oxide

A method for producing a catalyst for producing methacrylic acid, wherein the solid content is dispersed in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide.

[13] The method for producing a catalyst for producing methacrylic acid according to [11] or [12], wherein the solid content satisfies the following conditions (h) and (i).

(h) Solid content with an average crystal length of 2 to 50 μm as observed with an electron microscope.

(i) A solid content having an average aspect ratio of 2 to 30 as observed by an electron microscope.

(However, average aspect ratio = (average length of crystals) / (average diameter of crystals).)

[14] A method for producing methacrylic acid in which methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid according to any one of [1] to [10].

[15] A catalyst for producing methacrylic acid is prepared by the method described in any one of [11] to [13], and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. Method for producing acrylic acid.

[16] The method for producing methacrylic acid according to [14] or [15], wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas.

methacrolein:oxygen:water vapor:A=k:l:m:n (IV)

(In formula (IV), A represents nitrogen or helium. k to n represent the molar ratio of each gas, and when k + l + m + n = 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0≤m<45.)

[17] Production of methacrylic acid according to any one of [14] to [16], wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500 ° C. and the following formula (V) is satisfied. method.

15<W/F<550 (V)

(In formula (V), W represents the mass (g) of the metal oxide charged in the reactor, and F represents the supply amount (mol/h) of methacrolein per unit time.)

[18] Production of methacrylic acid according to any one of [14] to [17], wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500 ° C. and the following formula (VI) is satisfied. method.

0.00002<F/(S×W)<0.008 (VI)

(In formula (VI), S represents the BET specific surface area (m ² /g) of the metal oxide calculated by nitrogen adsorption, W represents the mass (g) of the metal oxide charged in the reactor, and F is It represents the supply amount (mol/h) of methacrolein per unit time.)

[19] A method for producing a methacrylic acid ester in which methacrylic acid produced by the method according to any one of [14] to [18] is esterified.

[20] A method for producing methacrylic acid ester, wherein methacrylic acid is produced by the method described in any one of [14] to [18], and the methacrylic acid is esterified.

[21] A catalyst for producing methacrylic acid characterized by containing a metal oxide satisfying the following conditions (b') and (c) as a catalyst used when producing methacrylic acid by oxidation of methacrolein. .

(b') A metal oxide containing a cyclic structure in which each of seven metal-oxygen octahedra (octahedral structure) is bonded.

(c) A metal oxide having a composition represented by formula (II) below.

Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)

(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0≤c<0.5, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)

[22] The catalyst for producing methacrylic acid according to [21], wherein 0<c<0.5 in the formula (II).

[23] The catalyst for producing methacrylic acid according to [21] or [22], wherein the metal oxide satisfies the following condition (d).

(d) A metal oxide that satisfies the following formula (III) when the mass of the metal oxide is M1 and the mass of the inactive component contained in the metal oxide is M2.

0≤M2/M1<0.05 (III)

[24] The catalyst for producing methacrylic acid according to any one of [21] to [23], wherein the metal oxide satisfies the following condition (e).

(e) Difference spectrum between the infrared absorption spectrum obtained by FT-IR measurement of the metal oxide and the infrared absorption spectrum obtained by FT-IR measurement after maintaining the metal oxide in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes The metal oxide having absorption peaks at 1557 ± 10 cm ^-1 , 1456 ± 10 cm ^-1 and 1374 ± 10 cm ^-1 .

[25] The catalyst for producing methacrylic acid according to any one of [21] to [24], wherein the metal oxide satisfies the following condition (f).

(f) A metal oxide having a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60 m ² /g.

[26] The catalyst for producing methacrylic acid according to any one of [21] to [25], wherein the metal oxide satisfies the following condition (g).

(g) A metal oxide showing diffraction peaks at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

[27] The catalyst for producing methacrylic acid according to [26], wherein the metal oxide satisfies the following condition (g1).

(g1) A metal oxide showing diffraction peaks only at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

[28] In the above condition (g), further 2θ = 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and the catalyst for producing methacrylic acid described in [26], which exhibits a diffraction peak at 27.4°±0.3°.

[29] In the above condition (g), further 2θ = 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and the catalyst for producing methacrylic acid described in [26], which exhibits a diffraction peak at 28.3°±0.3°.

[30] A catalyst for producing methacrylic acid containing a metal oxide satisfying the following conditions (c) and (g1) as a catalyst used when producing methacrylic acid by oxidation of methacrolein.

(c) A metal oxide having a composition represented by formula (II) below.

Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)

(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0≤c<0.5, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)

(g1) A metal oxide showing diffraction peaks only at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

[31] A method for producing the catalyst for producing methacrylic acid according to any one of [21] to [30],

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;

(2) Step of firing the solid content to obtain a metal oxide

Method for producing a catalyst for producing methacrylic acid comprising a.

[32] As a method for producing the catalyst for producing methacrylic acid according to [28] or [29],

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;

(1b) dispersing the solid content in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid content;

(2b) Step of firing the solid content obtained in (1b) to obtain a metal oxide

Method for producing a catalyst for producing methacrylic acid comprising a.

[33] The method for producing a catalyst for producing methacrylic acid according to [31] or [32], wherein the solid content satisfies the following conditions (h) and (i).

(h) Solid content with an average crystal length of 2 to 50 μm as observed with an electron microscope.

(i) A solid content having an average aspect ratio of 2 to 30 as observed by an electron microscope.

(However, average aspect ratio = (average length of crystals) / (average diameter of crystals).)

[34] A method for producing methacrylic acid in which methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid according to any one of [21] to [30].

[35] A catalyst for producing methacrylic acid is prepared by the method described in any one of [31] to [33], and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. Method for producing acrylic acid.

[36] The method for producing methacrylic acid according to [34] or [35], wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas.

methacrolein:oxygen:water vapor:A=k:l:m:n (IV)

(In formula (IV), A represents nitrogen or helium. k to n represent the molar ratio of each gas, and when k + l + m + n = 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0≤m<45.)

[37] Production of methacrylic acid according to any one of [34] to [36], wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500 ° C. and the following formula (V) is satisfied. method.

15<W/F<550 (V)

(In formula (V), W represents the mass (g) of the metal oxide charged in the reactor, and F represents the supply amount (mol/h) of methacrolein per unit time.)

[38] Production of methacrylic acid according to any one of [34] to [37], wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500 ° C. and the following formula (VI) is satisfied. method.

0.00002<F/(S×W)<0.008 (VI)

(In formula (VI), S represents the BET specific surface area (m ² /g) of the metal oxide calculated by nitrogen adsorption, W represents the mass (g) of the metal oxide charged in the reactor, and F is It represents the supply amount (mol/h) of methacrolein per unit time.)

[39] A method for producing a methacrylic acid ester in which methacrylic acid produced by the method according to any one of [34] to [38] is esterified.

[40] A method for producing methacrylic acid ester in which methacrylic acid is produced by the method described in [34] to [38] and the methacrylic acid is esterified.

[1'] A catalyst for producing methacrylic acid containing a metal oxide satisfying the following condition (a') as a catalyst used when producing methacrylic acid by gas phase catalytic oxidation of methacrolein.

(a') A cyclic structure comprising at least molybdenum and having a molar ratio represented by the following formula (I) formed by cyclic bonding of a metal-oxygen octahedron (octahedral structure) having a metal coordination number of 6; contain

(Sum of moles of Mo, V and X): (number of moles of O) = 7:35 (I)

(In formula (I), Mo, V and O represent molybdenum, vanadium and oxygen, respectively. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt represents at least one element selected from the group consisting of rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium.)

[2'] The catalyst for producing methacrylic acid according to [1'], wherein the metal oxide satisfies the following condition (c).

(c) A metal oxide having a composition represented by formula (II) below.

Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)

(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0≤c<0.5, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)

[3'] The catalyst for producing methacrylic acid according to [2'], wherein 0<c<0.5 in the formula (II).

[4'] The catalyst for producing methacrylic acid according to any one of [1'] to [3'], wherein the metal oxide satisfies the following condition (d).

(d) A metal oxide that satisfies the following formula (III) when the mass of the metal oxide is M1 and the mass of the inactive component contained in the metal oxide is M2.

0≤M2/M1<0.05 (III)

[5'] The catalyst for producing methacrylic acid according to any one of [1'] to [4'], wherein the metal oxide satisfies the following condition (e).

(e) Difference spectrum between the infrared absorption spectrum obtained by FT-IR measurement of the metal oxide and the infrared absorption spectrum obtained by FT-IR measurement after maintaining the metal oxide in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes The metal oxide having absorption peaks at 1557 ± 10 cm ^-1 , 1456 ± 10 cm ^-1 and 1374 ± 10 cm ^-1 .

[6'] The catalyst for producing methacrylic acid according to any one of [1'] to [5'], wherein the metal oxide satisfies the following condition (f).

(f) A metal oxide having a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60 m ² /g.

[7'] The catalyst for producing methacrylic acid according to any one of [1'] to [6'], wherein the metal oxide satisfies the following condition (g).

(g) A metal oxide showing diffraction peaks at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

[8'] The catalyst for producing methacrylic acid according to [7'], which shows diffraction peaks only at 2θ = 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in the above condition (g).

[9'] In the above condition (g), further 2θ = 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° The catalyst for producing methacrylic acid according to [7'], which shows diffraction peaks at ° and 27.4 ° ± 0.3 °.

[10'] In the above condition (g), 2θ = 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 The catalyst for producing methacrylic acid according to [7'], which shows diffraction peaks at ° and 28.3 ° ± 0.3 °.

[11'] A method for producing the catalyst for producing methacrylic acid according to any one of [1'] to [7'], [9'] and [10'], comprising the following steps (1) and (2) Method for producing a catalyst for producing methacrylic acid.

(1) A step of heating an aqueous solution or slurry containing at least molybdenum at 80 to 300°C for 3 to 200 hours to obtain a solid content.

(2) A step of firing the solid content to obtain a metal oxide.

[12'] A method for producing a catalyst for producing methacrylic acid according to [8'], comprising the following steps (1) and (2).

(1) A step of heating an aqueous solution or slurry containing at least molybdenum at 80 to 300°C for 3 to 200 hours to obtain a solid content.

(2) A step of firing the solid content to obtain a metal oxide.

[13'] After obtaining the solid content in the step (1) and before calcining the solid content in the step (2), the solid content is mixed with an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide solution The method for producing a catalyst for producing methacrylic acid according to [11'], including a dispersion treatment step of performing dispersion treatment in the inside.

[14'] In the step (2), any one of [11'] to [13'] wherein the solid content or the solid obtained after the dispersion treatment obtained in the dispersion treatment step satisfies the following conditions (h) and (i). The method for producing a catalyst for methacrylic acid production described in one.

(h) Solid content with an average crystal length of 2 to 50 μm as observed with an electron microscope.

(i) A solid content having an average aspect ratio of 2 to 30 as observed by an electron microscope.

(However, average aspect ratio = (average length of crystals) / (average diameter of crystals).)

[15'] A method for producing methacrylic acid in which methacrylic acid is produced by gas phase catalytic oxidation of methacrolein using the catalyst for producing methacrylic acid according to any one of [1'] to [10'].

[16'] A catalyst for producing methacrylic acid is prepared by the method described in any one of [11'] to [14'], and the catalyst for producing methacrylic acid is subjected to a gas phase catalytic oxidation reaction of methacrolein. Method for producing methacrylic acid for producing acrylic acid.

[17'] Production of methacrylic acid according to [15'] or [16'], wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500 ° C. and the following formula (V) is satisfied method.

15<W/F<550 (V)

(In formula (V), W represents the mass (g) of the metal oxide charged in the reactor, and F represents the supply amount (mol/h) of methacrolein per unit time.)

[18'] The methacrylic acid according to any one of [15'] to [17'], wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500°C and the following formula (VI) is satisfied. Method of making acid.

0.00002<F/(S×W)<0.008 (VI)

(In formula (VI), S represents the BET specific surface area (m ² /g) of the metal oxide calculated by nitrogen adsorption, W represents the mass (g) of the metal oxide charged in the reactor, and F is It represents the supply amount (mol/h) of methacrolein per unit time.)

[19'] The method for producing methacrylic acid according to any one of [15'] to [18'], wherein a gas having a composition represented by the following formula (IV') is supplied as a raw material gas.

methacrolein:oxygen:water vapor:A=k:l:m:n (IV')

(In formula (IV'), A represents nitrogen or helium. k to n represent the molar ratio of each gas, and when k + l + m + n = 100, 0.5 < k < 8.0, 2.0 < l <20.0, 4.5<m<45.)

[20'] A method for producing a methacrylic acid ester in which methacrylic acid produced by the method described in any one of [15'] to [19'] is esterified.

[21'] A method for producing methacrylic acid ester, wherein methacrylic acid is produced by the method described in any one of [15'] to [19'], and the methacrylic acid is esterified.

According to the present invention, a molybdenum-containing oxide catalyst having a high methacrylic acid yield used for oxidation of methacrolein and a method for producing the same, a method for producing methacrylic acid using the catalyst, and a production of methacrylic acid ester method can be provided.

1 is a diagram showing the molecular structure of a metal-oxygen octahedron (octahedral structure).
2 is a diagram showing a molecular structure when seven octahedral structures each share oxygen at an adjacent vertex to form a cyclic structure.
Fig. 3 is a diagram showing an example of a molecular structure on the ab plane of a metal oxide when the plane to which octahedral structures are cyclically bonded is the ab plane.

Hereinafter, the present invention will be described in detail.

[Catalyst for producing methacrylic acid]

One aspect of the catalyst for producing methacrylic acid according to the present invention includes a metal oxide containing molybdenum, and the metal oxide has a cyclic structure that satisfies the following conditions (a) and (b).

(a) A cyclic structure satisfying the following formula (I).

(Sum of moles of Mo, V and X): (number of moles of O) = 7:35 (I)

(In formula (I), Mo, V and O represent molybdenum, vanadium and oxygen, respectively. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt represents at least one element selected from the group consisting of rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium.)

(b) Cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygen at adjacent vertices.

In addition, another aspect of the catalyst for producing methacrylic acid according to the present invention contains a metal oxide that satisfies the following conditions (b') and (c).

(b') A metal oxide containing a cyclic structure in which 7 metal-oxygen octahedrons (octahedral structures) are each bonded (cyclic structures in which 7 octahedral structures are cyclically bonded).

(c) A metal oxide having a composition represented by formula (II) below.

Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)

(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0≤c<0.5, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)

In addition, another aspect of the catalyst for producing methacrylic acid according to the present invention contains a metal oxide that satisfies the above condition (c) and the following condition (g1).

(g1) A metal oxide showing diffraction peaks only at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

Details of each condition will be described below.

<Condition (a)>

The metal oxide having a cyclic structure that satisfies the condition (a) is determined by, for example, high angle annular dark field (HAADF) measurement using a scanning transmission electron microscope (STEM) (hereinafter referred to as "HAADF-STEM measurement"). ”) and the elemental species contained in the metal oxide.

The presence of the cyclic structure can be confirmed as a phase by observing the powder of the metal oxide using HAADF-STEM measurement.

The metal element species contained in the metal oxide can be identified by, for example, dissolving the metal oxide in ammonia water or hydrofluoric acid aqueous solution and analyzing by ICP emission spectrometry.

The reason why the cyclic structure confirmed on the HAADF-STEM image satisfies the above formula (I) is to determine the element appearing on the HAADF-STEM image from the contrast of the HAADF-STEM image and the metal element species contained in the metal oxide, and determine the cyclic structure. It can be confirmed by obtaining the ratio of each metal element in

On the other hand, when the metal oxide is composed of only components included in the formula (I), it can be determined that the cyclic structure satisfies the formula (I) when the existence of the cyclic structure is confirmed. In this case, the existence of the cyclic structure can be confirmed by the molecular probe method in the gas adsorption method in addition to confirming by the HAADF-STEM measurement of the metal oxide as described above.

In the case of using the molecular probe method in the gas adsorption method, the metal oxide is charged in a closed vacuum system, pretreated at 200 to 400°C, and then several types of gas molecules having different molecular diameters are introduced into the vacuum system as probes for adsorption. An isotherm is created and the pore diameter is calculated using the DA method (M. M. Dubinin, V. A. Astakhov, "Advances in Chemistry", 1971, Vol. 102, p. 69). If the calculated pore diameter is 0.35 to 0.5 nm, it can be judged that a cyclic structure exists.

In the above formula (I), from the viewpoint of methacrylic acid selectivity, X is niobium, tantalum, tungsten, manganese, iron, copper, cobalt, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium , at least one element selected from the group consisting of zinc, magnesium, and cerium, and more preferably at least one element selected from the group consisting of tungsten, iron, copper, antimony, and bismuth.

In the above formula (I), from the viewpoint of methacrylic acid yield, Mo, V and X preferably have a molar ratio represented by the following formula (I').

(Number of moles of Mo):(Number of moles of V):(Number of moles of X)=(7-a-b):a:b (I')

(In formula (I'), a and b are integers representing the molar ratio of vanadium and X, respectively, a = 0 to 3, more preferably a = 1 to 3 and b = 0 to 3.)

The values of a and b can be specified by performing Rietvelt analysis on the X-ray diffraction pattern of the metal oxide measured, for example, by X-ray structural analysis.

<Conditions (b) and (b')>

The molecular structure of the metal-oxygen octahedron (octahedral structure) is shown in FIG. 1, a metal element (Mo, V or X) having a coordination number of 6 is located at the center of the octahedral structure, and oxygen is located at all vertices of the octahedron. Further, FIG. 2 shows a molecular structure when each of the 7 octahedral structures shown in FIG. 1 is bonded to each other by sharing oxygen at adjacent vertices to form a cyclic structure.

In the oxidation of methacrolein, the cyclic structure shown in Fig. 2 has high catalytic activity. It is speculated that this is because an adsorption site capable of producing methacrylic acid with high selectivity from methacrolein is formed by the presence of the cyclic structure. In addition, the catalyst performance can be controlled by controlling the type, combination and amount of metal elements included in the cyclic structure. On the other hand, a structure containing Mo, V or X may be disposed in the pores formed by the cyclic structure.

The cyclic structure shown in FIG. 2 corresponds to a part of the structure of the metal oxide. In Fig. 2, Fig. 3 shows an example of the molecular structure of the ab plane of the metal oxide when the plane to which the octahedral structures are cyclically bonded is the ab plane. In Fig. 3, the annular structure shown in Fig. 2 is bonded to another annular structure by sharing an oxygen at a vertex. In addition, the cyclic structure in which octahedral structures are cyclically bonded is arranged sharing one octahedral structure with another adjacent cyclic structure. On the other hand, the metal oxide may have a cyclic structure in which six or less octahedral structures are bonded by sharing oxygens at adjacent vertices.

That the metal oxide has a cyclic structure satisfying the above condition (b) can be confirmed by, for example, HAADF-STEM measurement or a molecular probe method in a gas adsorption method.

In the case of using HAADF-STEM measurement, the existence of a cyclic structure satisfying the above condition (b) can be confirmed as a phase by observing the metal oxide powder.

In the case of using the molecular probe method in the gas adsorption method, the metal oxide is filled in a closed vacuum system, pretreated at 200 to 400°C, and CO ₂ and CH are probes that can be adsorbed into pores with a diameter of 0.40 to 0.43 nm. An adsorption isotherm can be created by introducing ₄ or C ₂ H ₆ into a vacuum system, and the pore diameter can be calculated using the DA (Dubinin-Astakhov) method (MM Dubinin, VA Astakhov, “Advances in Chemistry”, 1971 , Volume 102, p. 69). If the calculated pore diameter is 0.40 to 0.43 nm, it can be judged that a cyclic structure satisfying the above condition (b) exists.

Further, that the metal oxide has a cyclic structure satisfying condition (b) indicates that the metal oxide satisfies condition (b').

<Condition (c)>

The molar ratio of each element in the metal oxide can be calculated by completely dissolving the metal oxide in aqueous ammonia, nitric acid, hydrochloric acid, sulfuric acid, aqua regia or hydrofluoric acid and analyzing by ICP emission spectrometry.

In addition, the molar ratio of the ammonium group can be calculated by analyzing the metal oxide by the Kjeldahl method. On the other hand, in the present invention, "ammonium root" means a generic term for ammonia (NH ₃ ) that can become an ammonium ion (NH ₄ ⁺ ) and ammonium contained in ammonium-containing compounds such as ammonium salts.

In the formula (II), from the viewpoint of methacrylic acid selectivity, the molar ratio of vanadium is preferably 0<c<0.5.

In the above formula (II), from the viewpoint of methacrylic acid selectivity, X is niobium, tantalum, tungsten, manganese, iron, copper, cobalt, phosphorus, arsenic, antimony, tellurium, bismuth, boron, It is preferably at least one element selected from the group consisting of indium, zinc, magnesium and cerium, and more preferably at least one element selected from the group consisting of tungsten, iron, copper, antimony and bismuth.

In addition, when the metal oxide has a cyclic structure that satisfies the conditions (a) and (b), and when the metal oxide satisfies the conditions (b') and (c), the metal oxide further It is preferable to satisfy the following condition (g).

(g) A metal oxide showing diffraction peaks at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

<Conditions (g) and (g1)>

In the X-ray diffraction pattern (using Cu-Kα rays), the diffraction peak appearing at 2θ = 22.1° ± 0.3° originates from the (001) plane of the crystal structure of the metal oxide, and at 2θ = 45.2° ± 0.3° The emerging diffraction peak originates from the (002) plane. When the c-axis is the axis perpendicular to the above-described ab-plane, the presence of these diffraction peaks indicates that the metal oxide has a structure in which the metal oxides are regularly layered in the c-axis direction. When the metal oxide satisfies the condition (g), it means that the ab planes are laminated at intervals of 0.396 to 0.410 nm in the metal oxide. On the other hand, the diffraction peak is assumed to have a height of 5/100 or more of the peak of maximum intensity appearing within the range of 2θ = 2 to 60°.

In condition (g), when the following condition (g1) is further satisfied, it can be specified that the metal oxide has an amorphous structure.

(g1) A metal compound showing diffraction peaks only at 2θ=22.1°±0.3° and 45.2°±0.3° in an X-ray diffraction pattern (using Cu-Kα rays).

Further, in condition (g), in addition to 2θ = 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 °, 2θ = 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 ° , 26.9°±0.3°, 27.2°±0.3°, and 27.4°±0.3°, it can be specified that the metal oxide has an orthorhombic crystal structure. Further, in addition to 2θ=22.1°±0.3° and 45.2°±0.3°, 2θ=4.7°±0.3°, 8.3°±0.3°, 25.3°±0.3°, 25.7°±0.3°, 27.0°±0.3° , 27.9°±0.3° and 28.3°±0.3°, it can be specified that the metal oxide has a trigonal crystal structure. From the viewpoint of methacrylic acid yield, it is preferable that the metal oxide has an amorphous structure, an orthorhombic crystal structure, or a trigonal crystal structure.

From the viewpoint of methacrylic acid yield, the metal oxide preferably further satisfies at least one selected from the following conditions (d) to (f), and satisfies all of the following conditions (d) to (f). It is more preferable to

(d) A metal oxide that satisfies the following formula (III) when the mass of the metal oxide is M1 and the mass of the inactive component contained in the metal oxide is M2.

0≤M2/M1<0.05 (III)

(e) Difference spectrum between the infrared absorption spectrum obtained by FT-IR measurement of the metal oxide and the infrared absorption spectrum obtained by FT-IR measurement after maintaining the metal oxide in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes The metal oxide having absorption peaks at 1557 ± 10 cm ^-1 , 1456 ± 10 cm ^-1 and 1374 ± 10 cm ^-1 .

(f) A metal oxide having a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60 m ² /g.

Details of each condition will be described below.

<Condition (d)>

In the formula (III), M2/M1 represents the mass ratio of the inactive component contained in the metal oxide. The inactive component is a compound that does not show catalytic activity or has extremely low catalytic activity when methacrolein is oxidized at a reaction temperature of 180 to 500°C. Examples of the inactive component include compounds such as Al ₂ O ₃ , SiO ₂ , TiO ₂ , zeolites and other catalyst carrier compounds.

When M2/M1 satisfies the above formula (III), since the ratio of the active ingredient per unit volume in the metal oxide is sufficiently high, the desired methacrolein conversion rate and continuous operation time are achieved in the production of methacrylic acid. it becomes easier to do

<Condition (e)>

The apparatus used for FT-IR measurement is not particularly limited, as long as it can measure a range of at least 1200 to 2000 cm ^-1 . The measurement method may be either a transmission method or a diffuse reflection method, and the metal oxide may be diluted with a diluent before measurement. As the diluent, a substance that does not exhibit infrared absorption in the range of at least 1200 to 2000 cm ^-1 can be used. As a diluent, KBr is mentioned, for example. The FT-IR measurement of the metal oxide is performed by installing the metal oxide in an apparatus, performing pretreatment at 300° C. or higher for 10 minutes or more under nitrogen or helium flow, and then cooling to the measurement temperature. Subsequently, the metal oxide was held for 5 to 60 seconds in a water vapor atmosphere of 15 to 25% by volume, and after further holding for 60 minutes in a methacrolein atmosphere of 2.0% by volume or more, FT-IR measurement was performed, and the difference spectrum from the difference between the two get In the difference spectrum, when it has absorption peaks at 1557±10cm ^-1 , 1456±10cm ^-1 and 1374±10cm ^-1 , methacrylic acid can be produced with a higher methacrylic acid selectivity. On the other hand, the absorption peak is defined as having a value of 0.1 or more in the peak area when the horizontal axis is the wavelength and the vertical axis is the absorbance detected by FT-IR measurement.

<Condition (f)>

The BET specific surface area S can be calculated by nitrogen adsorption measurement using nitrogen as a probe in the gas adsorption method. Nitrogen adsorption measurement is performed by filling the metal oxide in a closed vacuum system, performing pretreatment at 200 to 400 ° C, adsorbing nitrogen to the metal oxide at liquid nitrogen temperature, drawing an adsorption isotherm, and calculating the specific surface area by the BET method. do. When the BET specific surface area S of the metal oxide is 1.5 m ² /g or more, the conversion rate of methacrolein in the production of methacrylic acid is improved. In addition, when the BET specific surface area S is 60 m ² /g or less, the amount of heat generated in the production of methacrylic acid can be suppressed, and operation can be continued stably.

[Method for producing a catalyst for producing methacrylic acid]

One aspect of the method for producing a catalyst for methacrylic acid production according to the present invention includes the following steps (1) and (2).

(1) A step of heating an aqueous solution or slurry containing at least molybdenum at 80 to 300°C for 3 to 200 hours to produce a solid content.

(2) A step of firing the solid content to obtain a metal oxide.

In addition, another aspect of the method for producing a catalyst for methacrylic acid production according to the present invention includes the following steps (1), (1b) and (2b).

(1) A step of heating an aqueous solution or slurry containing at least molybdenum at 80 to 300°C for 3 to 200 hours to produce a solid content.

(1b) A step of dispersing the solid content in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid content after the dispersion treatment.

(2b) A step of baking the solid content after the dispersion treatment to obtain a metal oxide.

Hereinafter, the detail of each process is demonstrated.

(Process (1))

In step (1), a solution or slurry is prepared by mixing a part or all of a catalyst raw material containing at least molybdenum with a solvent, heating the solution or slurry at 80 to 300°C for 3 to 200 hours, and solid content generate When a part of the catalyst raw material is mixed with a solvent to prepare the solution or slurry, the remaining catalyst raw material may be mixed after preparing the solution or slurry.

<Catalyst raw material>

The catalyst raw material is not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halides and the like of each element included in the composition of the target metal oxide can be used in combination.

Examples of molybdenum raw materials include ammonium heptamolybdate, molybdenum trioxide, molybdic acid, and molybdenum chloride, and molybdenum-based polyoxometallates and the like can also be used. As the molybdenum-based polyoxometallate, heteropolyacids, isopolyacids, and raw materials obtained by modifying heteropolyacids and isopolyacids with alkylammonium ions can be used. As a raw material obtained by modifying an isopoly acid with an alkylammonium ion, (CH ₃ NH ₃ ) ₆ Mo ₇ O ₂₄ , (C ₂ H ₅ NH ₃ ) Mo ₃ O ₁₀ , or the like can be used.

The catalyst raw material preferably contains vanadium, and examples of the vanadium raw material include vanadyl sulfate, vanadium sulfate, vanadium pentoxide, ammonium metavanadate, and vanadium chloride. In addition, a surfactant may be added as a catalyst raw material. Examples of the surfactant include anionic surfactants and cationic surfactants, and examples of the cationic surfactant include sodium dodecyl sulfate and the like.

<Solvent>

As the solvent, water and organic solvents can be used, but it is preferable to use water from the viewpoint of ease of handling and safety. The mass of the solvent is preferably 500 to 5000 parts by mass with respect to 100 parts by mass in total of the catalyst raw materials used for preparation of the solution or slurry.

<Preparation of solution or slurry>

The solution or slurry is prepared by mixing the catalyst raw material in the solvent. The mixing method is not particularly limited, but a method in which the catalyst raw material is added to the solvent and mixed by stirring is preferable. The order of addition is not particularly limited and can be set appropriately.

In the step (2) described later, from the viewpoint of forming a metal oxide having a cyclic structure that satisfies the condition (a), the solution or slurry is preferably prepared using a component included in the formula (I) do.

In addition, a trace amount of a metal oxide having a composition represented by the formula (II) may be added to the solution or slurry. By adding the metal oxide in advance, the methacrylic acid yield of the finally obtained catalyst is improved.

In the step (2) described later, from the viewpoint of forming a metal oxide having a cyclic structure that satisfies the condition (b), the pH of the solution or slurry is set to 1.7 to 3.5, and nitrogen, hydrogen or helium is bubbling It is desirable to do The pH of the solution or slurry can be adjusted by, for example, using aqueous ammonia or sulfuric acid as a raw material for the catalyst. On the other hand, the pH of the solution or slurry can be measured by a portable pH meter D-72 (product name) manufactured by HORIBA or the like.

<Generation of solid content>

Subsequently, by heating the solution or slurry, a solid content is produced. The heating temperature of the solution or slurry is preferably 80 to 300°C. When the heating temperature is 80°C or higher, in step (2) described later, a metal oxide having a cyclic structure satisfying the condition (b) can be formed advantageously. Moreover, when the heating temperature is 300°C or lower, the methacrylic acid yield of the finally obtained catalyst is improved. The lower limit of the heating temperature is more preferably 120°C or higher, and more preferably 175°C or higher. Moreover, as for the upper limit of heating temperature, 260 degrees C or less is more preferable, and 230 degrees C or less is still more preferable.

As for the heating time of the said solution or slurry, 3 to 200 hours are preferable from a viewpoint of methacrylic acid yield. The lower limit of the heating time is more preferably 10 hours or more, and the upper limit is more preferably 72 hours or less.

A sheet made of Teflon (registered trademark), a glass plate, or the like may be put into the solution or slurry beforehand and heated. Since orthorhombic and trigonal structures tend to be easily formed on the surface of Teflon, the formation of these crystal structures is promoted by inserting a Teflon sheet or glass plate.

<Generation of solid content by hydrothermal method>

From the viewpoint of the methacrylic acid yield of the obtained catalyst, it is preferable to produce solid content using a hydrothermal method capable of suppressing evaporation of water. The hydrothermal method is a method of synthesizing a compound in the presence of high-temperature and high-pressure hot water, and reacting by heating and pressurizing raw materials and water in an airtight container called an autoclave. For the hydrothermal method, a pressure vessel such as an autoclave can be used. The container may be left still or rotated, and electromagnetic waves may be irradiated from the outside of the container.

In the case of using the hydrothermal method, the structure of the produced solid content can be controlled by the concentration of the molybdenum raw material used and the pH of the solution or slurry. For example, when using ammonium heptamolybdate as a molybdenum raw material, the concentration of ammonium heptamolybdate relative to the solvent is 0.02 to 0.04 mol/L, and the pH of the solution or slurry is 2.3 to 3.5 By setting the pH to 1.7 to 2.3, the formation of a trigonal structure tends to be promoted. In addition, the formation of an amorphous structure tends to be promoted by setting the concentration of ammonium heptamolybdate to 0.05 to 0.30 mol/L relative to the solvent and setting the pH of the solution or slurry to 1.7 to 3.5.

<Drying of solution or slurry>

After generation of the solid content, the solution or slurry may be dried using suction filtration, centrifugal separation, drum dryer, spray dryer, etc. to obtain the solid content. When suction filtration or centrifugation is used, it is preferable to further remove moisture at 20 to 150°C to obtain solid content.

(Step (1b))

In the method for producing a catalyst for producing methacrylic acid according to the present invention, when the metal oxide has an orthorhombic or trigonal crystal structure, the solid content produced in the step (1) is mixed with an aqueous solution of oxalic acid, hydrochloric acid, ethylene A step (1b) of dispersing treatment in glycol or aqueous hydrogen peroxide may be included. When the solid content contains a component having a hexagonal crystal structure or a pseudohexagonal structure, etc., the yield may decrease in the production of methacrylic acid. By subjecting the solid content to a dispersion treatment in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide, components having a hexagonal or quasi-hexagonal structure are eluted, and these components can be separated from the solid content.

On the other hand, since the component which has an amorphous structure is also eluted by process (1b), when the said metal oxide has an amorphous structure, it is preferable to manufacture a catalyst for methacrylic acid production, without performing process (1b).

The solid content produced in the step (1) or the solid content after dispersion treatment obtained in the step (1b) (hereinafter collectively referred to as "solid content") satisfies the following conditions (h) and (i). desirable.

(h) Solid content with an average crystal length of 2 to 50 μm as observed with an electron microscope.

(i) A solid content having an average aspect ratio of 2 to 30 as observed by an electron microscope.

(However, average aspect ratio = (average length of crystals) / (average diameter of crystals).)

<condition (h) and condition (i)>

The electron microscope used to observe the average length and average aspect ratio of the crystal is not limited, as long as it can identify 0.1 to 50 μm, discern at least 2 to 50 μm, and measure the length. Observation by fixing the solid content on a carbon tape, a grid or mesh for an electron microscope using, for example, a scanning electron microscope (SEM), a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), or the like. can do.

In the conditions (h) and (i), the average length of the crystals represents the average length of the observed crystals in the major axis direction, and the average diameter of the crystals represents the average value of the observed lengths of the crystals in the minor axis direction. The length of the crystal in the major axis direction and the minor axis direction is obtained by manually measuring the length considering the scale or by measuring the length by image analysis. In either case of manual and image analysis, at least 500 different crystals whose crystal lengths can be identified are extracted, and the lengths in the major axis direction and minor axis direction measured for all the extracted crystals are obtained. The average length of the crystals is calculated by obtaining the average value of the obtained lengths in the major axis direction, and the average diameter of the crystals is calculated by finding the average value of the lengths in the minor axis direction. However, when the cross section of the crystal in the minor axis direction is not a perfect circle, the length in the minor axis direction is calculated from the cross section in the minor axis direction using the following formula.

The average diameter of the crystals and the average aspect ratio of the crystals can be controlled by adding a surfactant as a catalyst raw material in the step (1). When the addition amount of the surfactant is increased, the average diameter of the crystals of the solid content increases and the average aspect ratio decreases. In addition, the average length of the crystals and the average aspect ratio of the crystals can be controlled by pulverizing the solid content. If the pulverization time is long, the crystals are physically destroyed, the average length of the crystals becomes small, and the average aspect ratio becomes small. Grinding can be carried out using, for example, a mortar, ball mill, high-speed rotary mill, jet mill, mine blaster or the like.

The average length of the crystals is preferably 0.1 μm or more, more preferably 0.2 μm or more, still more preferably 1 μm or more, especially under condition (h) (2 μm or more), from the viewpoint of stably maintaining the cyclic structure. It is desirable to satisfy

In the condition (h), when the average length of the crystal is 2 μm or more, the cyclic structure satisfying the conditions (a) and (b) can stably maintain the structure, and in the production of methacrylic acid by a simple method can improve the continuous operation time of In addition, when the average length of the crystals is 50 μm or less, in the production of methacrylic acid, the cross section of the crystals in the short axis direction can be effectively used, and the yield of methacrylic acid is improved. From these viewpoints, the average length of the crystals is more preferably 3 μm or more, still more preferably 5 μm or more, and preferably 40 μm or less, and more preferably 30 μm or less.

In condition (i), if the average aspect ratio of the crystal is 2 to 30, it is easy to suppress the collapse of the cyclic structure satisfying the above conditions (a) and (b), and the cyclic structure in the production of methacrylic acid Since can contribute effectively to the reaction, the yield of methacrylic acid is improved.

(Forming process)

The manufacturing method of the catalyst for methacrylic acid production concerning this invention may also include the molding process of shape|molding the said solid content before the process (2) or process (2b) mentioned later. By shaping the said solid content, the pressure loss in a reactor in methacrylic acid production is reduced and the influence of raw material gas diffusion is suppressed, and the selectivity of methacrylic acid improves.

The molding method is not particularly limited, and a known dry or wet molding method can be applied. As a molding method, tablet molding, extrusion molding, pressure molding, rolling granulation, etc. are mentioned, for example. The shape of the solid content after molding is not particularly limited, and may be any shape such as a spherical granular shape, a ring shape, a cylindrical pellet shape, a molded shape, and a granular shape obtained by pulverization and classification after molding. The size of the solid content after molding is preferably 0.1 to 10 mm in diameter. When the diameter is 0.1 mm or more, the pressure loss in the reactor can be made sufficiently small in the production of methacrylic acid. Moreover, when the diameter is 10 mm or less, the methacrolein conversion rate is improved. It is more preferable that the lower limit of the diameter is 3 mm or more and the upper limit is 8 mm or less.

(Step (2) and Step (2b))

In step (2) and step (2b), the solid content or the solid content after molding obtained in the molding step is fired to obtain a metal oxide. The methacrolein conversion rate in methacrylic acid manufacture can be improved by baking the said solid content or the solid content after shaping|molding obtained by the said shaping|molding process. On the other hand, in step (2), when the solid content is the solid content produced in the step (1), and in step (2b), the solid content is the solid content after dispersion treatment obtained in the step (1b).

The firing method is not particularly limited, and a suitable method may be appropriately selected from stationary firing, flow firing, and the like. As stationary firing, a method of firing using, for example, a box-shaped electric furnace, an annular firing furnace, or the like is exemplified. As fluid firing, a method of firing using, for example, a fluid firing furnace, a rotary kiln, or the like is exemplified. Firing gas is performed in an atmosphere of an oxygen-containing gas such as air or an inert gas, for example. On the other hand, "inert gas" represents a gas that does not reduce the catalytic activity in the production of methacrylic acid, and examples thereof include nitrogen, carbon dioxide gas, helium, and argon. These may use 1 type, and may mix and use 2 or more types. As for the firing atmosphere, as long as a desired firing gas atmosphere can be maintained, the firing gas may or may not be circulated. From the viewpoint of forming a metal oxide having a cyclic structure that satisfies the above conditions (a) and (b), the firing temperature is preferably 200 to 500°C. The lower limit of the firing temperature is more preferably 300°C or higher, and the upper limit is more preferably 470°C or lower. Moreover, as for baking time, 1 to 40 hours are preferable.

[Method for producing methacrylic acid]

The method for producing methacrylic acid according to the present invention is a method for producing methacrylic acid by oxidation of methacrolein using the catalyst for producing methacrylic acid according to the present invention. In addition, in the method for producing methacrylic acid according to the present invention, a catalyst for producing methacrylic acid is prepared by the method according to the present invention, and methacrylic acid is obtained by oxidation of methacrylic acid using the catalyst for producing methacrylic acid. way to manufacture it. The oxidation can be performed by filling a reactor with a catalyst for producing methacrylic acid containing the metal oxide and supplying a raw material gas containing methacrolein to the reactor.

<Charge of Catalyst>

The catalyst for producing methacrylic acid may contain a known oxidation catalyst such as polyoxometallate in addition to the above metal oxide, but from the viewpoint of the continuous operation time in production of methacrylic acid, the above metal oxide is 80% by mass or more. It is preferable to contain, and it is more preferable to contain 90% or more of the said metal oxide. The catalyst layer may be one layer, or may be filled with a plurality of catalysts having different activities divided into a plurality of layers, respectively. In addition, for heat removal, it is preferable to mix with an inert diluent such as sea sand or silicon carbide.

<Supply of Source Gas>

The source gas may be obtained by diluting methacrolein and molecular oxygen with an inert gas such as nitrogen or carbon dioxide gas. Additionally, water vapor may be added to the raw material gas.

As the raw material gas, it is preferable to supply a gas having a composition represented by the following formula (IV).

methacrolein:oxygen:water vapor:A=k:l:m:n (IV)

(In formula (IV), A represents nitrogen or helium. k to n represent the molar ratio of each gas, and when k + l + m + n = 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0≤m<45.)

In formula (IV), k to m are preferably 2.0 < k < 4.0, 5.0 < l < 12.0, and 0 ≤ m < 25 from the viewpoint of methacrylic acid selectivity.

Also, from the viewpoint of utility cost, the upper limit of m is preferably 10 or less. Thereby, the raw material cost in methacrylic acid production is reduced. In addition, since the amount of wastewater is reduced, the cost required for wastewater treatment is reduced. As for the upper limit of m, it is more preferable that it is 5 or less, and m=0 is still more preferable.

In addition, it is preferable to supply a raw material gas containing methacrolein so as to satisfy at least one selected from the following formulas (V) and (VI), and methacrolein to satisfy the following formulas (V) and (VI). It is more preferable to supply source gas containing a lane.

15<W/F<550 (V)

(In formula (V), W represents the mass (g) of the metal oxide charged in the reactor, and F represents the supply amount (mol/h) of methacrolein per unit time.)

0.00002<F/(S×W)<0.008 (VI)

(In formula (VI), S represents the BET specific surface area (m ² /g) of the metal oxide calculated by nitrogen adsorption, W represents the mass (g) of the metal oxide charged in the reactor, and F is It represents the supply amount (mol/h) of methacrolein per unit time.)

In the formula (V), W/F represents the contact time between the catalyst and methacrolein charged in the reactor. When W/F exceeds 15, excessive heat generation of the catalyst in methacrylic acid production can be suppressed. In addition, when W/F is less than 550, catalyst cost can be suppressed. The lower limit of W/F is more preferably 20 or more, more preferably 40 or more, particularly preferably 50 or more, and most preferably 80 or more. The upper limit of W/F is more preferably 500 or less, more preferably 400 or less, and particularly preferably 270 or less.

In the formula (VI), F/(S×W) represents the supplied amount of methacrolein per specific surface area of the catalyst. When F/(S×W) exceeds 0.00002, it is possible to suppress the size of a reactor required to secure desired methacrylic acid production. In addition, when F/(S×W) is less than 0.008, catalyst cost can be suppressed. The lower limit of F/(S×W) is more preferably 0.00007 or more. The upper limit of F/(S×W) is more preferably 0.005 or less, further preferably 0.001 or less, and particularly preferably 0.0008 or less.

<Reaction temperature and pressure>

The reaction temperature is preferably 180 to 500°C, the lower limit is 200°C or more, and the upper limit is more preferably 400°C or less. The reaction pressure is preferably 0.1 to 1 MPa (G). However, (G) means that it is a gauge pressure.

[Method for producing methacrylic acid ester]

The method for producing methacrylic acid ester according to the present invention is a method of esterifying methacrylic acid produced by the method according to the present invention. In addition, the method for producing methacrylic acid ester according to the present invention is a method of producing methacrylic acid by the method according to the present invention and esterifying the methacrylic acid. According to these methods, methacrylic acid ester can be obtained using methacrylic acid obtained by oxidation of methacrolein. It does not specifically limit as methacrylic acid and the alcohol made to react, Methanol, ethanol, isopropanol, n-butanol, isobutanol, etc. are mentioned. As methacrylic acid ester obtained, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate etc. are mentioned, for example. The reaction can be performed in the presence of an acidic catalyst such as a sulfonic acid type cation exchange resin. As for reaction temperature, 50-200 degreeC is preferable.

Example

Hereinafter, the present invention will be specifically described using Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Measurement of Average Length and Average Aspect Ratio of Crystals)

For the average length and average aspect ratio of crystals in the solid content, the lengths of at least 500 crystals in the major axis direction and minor axis direction were manually measured using an SEM (product name: JSM-7400F, manufactured by JEOL), and an average value was obtained. calculated by doing

(Measurement of pore diameter by molecular probe method)

The pore diameter of the metal oxide is determined by pretreating the metal oxide at 300°C, and then drawing an adsorption isotherm by a molecular probe method using CO ₂ , CH ₄ , or C ₂ H ₆ (product name: BELSORP-MAX, Microtrac). Belze), calculated using the DA method.

(Measurement of X-ray diffraction pattern)

The X-ray diffraction pattern of the metal oxide was measured using Cu-Kα rays with an X-ray structure analyzer (product name: RINT Ultima ⁺ , manufactured by Rigaku, tube voltage: 40 kV, tube current: 20 mA). Regarding the obtained X-ray diffraction pattern, when diffraction peaks were shown only at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3°, it was specified that it had an amorphous structure. Further, in addition to 2θ=22.1°±0.3° and 45.2°±0.3°, 2θ=6.6°±0.3°, 7.9°±0.3°, 9.0°±0.3°, 26.4°±0.3°, 26.9°±0.3° , 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 °, when showing diffraction peaks, it was specified that it had an orthorhombic crystal structure. Further, in addition to 2θ=22.1°±0.3° and 45.2°±0.3°, 2θ=4.7°±0.3°, 8.3°±0.3°, 25.3°±0.3°, 25.7°±0.3°, 27.0°±0.3° , 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 °, when showing diffraction peaks, it was specified that it had a trigonal crystal structure. Regarding the crystal structure other than the amorphous structure, the orthorhombic crystal structure, and the trigonal crystal structure, the crystal structure was specified by carrying out a search and match analysis with a notated XRD pattern. Search and match analysis was performed using the notational XRD pattern data recorded in ICDD2017 using the analysis software JADE 9.8.

(calculation of molar ratio)

The molar ratio of each element in the metal oxide was calculated by dissolving the metal oxide component in ammonia water or hydrofluoric acid aqueous solution and analyzing by ICP emission spectrometry. The molar ratio of the ammonium root was determined by analyzing the metal oxide by the Kjeldahl method. On the other hand, when the solid content is recovered by suction filtration, since a part of the metal component is eluted to the filtrate side, the molar ratio calculated from the input ratio of the raw materials and the molar ratio calculated by performing the above-described analysis of the obtained metal oxide are necessarily don't match

(Calculation of difference spectrum by FT-IR measurement)

The FT-IR measurement of the metal oxide (product name: FT/IR-6100, manufactured by Nippon Spectroscopy) was performed by a transmission method. First, 40 to 50 mg of metal oxide in the form of pellets with a diameter of 20 mm was placed in an apparatus, heated to 400 ° C. at 10 ° C./min under helium circulation, and pretreatment was performed for 10 minutes. Thereafter, the metal oxide was cooled to 100°C, and an infrared absorption spectrum was measured (FT-IR measurement 1). Next, the metal oxide is held for 10 seconds in a water vapor atmosphere of 20% by volume, methacrolein is further introduced so as to have a methacrolein atmosphere of 2.0% by volume or more, the circulation gas is converted to oxygen, maintained for 60 minutes, and infrared The absorption spectrum was measured (FT-IR measurement 2). The difference spectrum was calculated by subtracting the infrared absorption spectrum obtained by FT-IR measurement 1 from the infrared absorption spectrum obtained by FT-IR measurement 2.

(Measurement of BET specific surface area)

The BET specific surface area S of the metal oxide was calculated using the BET method after pretreating the metal oxide at 300°C, creating a nitrogen adsorption isotherm (product name: BELSORP-MAX, manufactured by Microtrac Bell).

(analysis of source gas and product)

The raw gas and product were analyzed using gas chromatography (apparatus: GC-14B manufactured by Shimadzu Corporation, column: Porapak-QS). From the results of gas chromatography, the conversion rate of methacrolein, the selectivity of methacrylic acid to be produced, and the yield of methacrylic acid were determined by the following equations.

Methacrolein conversion rate (%) = (β / α) × 100

Methacrylic acid selectivity (%) = (γ / β) × 100

Methacrylic acid yield (%) = (γ / α) × 100

In the formula, α represents the number of moles of methacrolein supplied, β represents the number of moles of methacrolein reacted, and γ represents the number of moles of methacrylic acid produced.

[Production Example 1]

A solution obtained by adding 8.83 g of ammonium heptamolybdate tetrahydrate to 120 g of pure water and stirring at room temperature was mixed with a solution obtained by adding 3.29 g of vanadyl sulfate to 120 g of pure water and stirring at room temperature, and the mixture was stirred for 10 minutes. The pH at this time was 3.19. The obtained mixed solution was transferred to a Teflon autoclave in which a Teflon sheet was previously inserted, and bubbling was performed with nitrogen at a flow rate of 50 L/min for 10 minutes. Thereafter, solid content was produced using a hydrothermal method in a 175°C oven for 48 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was mixed with 1.26 g of oxalic acid dihydrate and 25 g of pure water with respect to 1.0 g of solid content, followed by dispersion mixing at 60°C for 30 minutes. Thereafter, while washing well with 500 g of pure water, solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar. With respect to the obtained solid content after the pulverization treatment, the average length and average aspect ratio of the crystals were measured. The results are shown in Table 1.

Subsequently, the solid content after the pulverization treatment was calcined at 400°C for 2 hours under nitrogen flow at 50 mL/min to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygens at adjacent vertices. It became. In addition, it was confirmed that the metal oxide satisfies the above formula (II). Table 1 shows the mass ratio M2/M1 of the inactive component, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 2]

Solid content after dispersion treatment was obtained by the same method as in Production Example 1. The solid content after the dispersion treatment was not subjected to pulverization, and the average length and average aspect ratio of the crystals were measured. The results are shown in Table 1.

Subsequently, the solid content after the dispersion treatment was fired by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are each bonded by sharing oxygen at adjacent vertices. . In addition, it was confirmed that the metal oxide satisfies the above formula (II). Table 1 shows the mass ratio M2/M1 of the inactive component, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 3]

A solution obtained by adding 8.83 g of ammonium heptamolybdate tetrahydrate to 120 g of pure water and stirring at room temperature was mixed with a solution obtained by adding 3.29 g of vanadyl sulfate to 120 g of pure water and stirring at room temperature, and the mixture was stirred for 10 minutes. Subsequently, the pH was adjusted to 2.30 by adding 2M sulfuric acid. The obtained mixed solution was transferred to a Teflon autoclave in which a Teflon sheet was previously inserted, and bubbling was performed with nitrogen at a flow rate of 50 L/min for 10 minutes. Thereafter, the solid content was purified using a hydrothermal method in a 175°C oven for 20 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was mixed with 1.26 g of oxalic acid dihydrate and 25 g of pure water with respect to 1.0 g of solid content, followed by dispersion mixing at 60°C for 30 minutes. Thereafter, while washing well with 500 g of pure water, solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar. With respect to the obtained solid content after the pulverization treatment, the average length and average aspect ratio of the crystals were measured. The results are shown in Table 1.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are each bonded by sharing oxygen at adjacent vertices. . In addition, it was confirmed that the metal oxide satisfies the above formula (II). Table 1 shows the mass ratio M2/M1 of the inactive component, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 4]

A solution obtained by adding 17.7 g of ammonium heptamolybdate tetrahydrate to 120 g of pure water and stirring at room temperature was mixed with a solution obtained by adding 6.58 g of vanadyl sulfate to 120 g of pure water and stirring at room temperature, and stirred for 10 minutes. The pH at this time was 3.26. The obtained mixed solution was transferred to a Teflon autoclave and bubbled with nitrogen at a flow rate of 50 L/min for 10 minutes. Thereafter, solid content was produced using a hydrothermal method in a 175°C oven for 48 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygens at adjacent vertices. It became. In addition, it was confirmed that the metal oxide had an amorphous structure that satisfied the above formula (II) and showed diffraction peaks only at 2θ = 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in the X-ray diffraction pattern. Table 1 shows the mass ratio M2/M1 of the inactive component, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 5]

To a solution obtained by adding 28.04 g of pure water to 28.04 mL of a 70% ethylamine solution, 21.594 g of molybdenum trioxide was added and completely dissolved, followed by evaporation to obtain (C ₂ H ₅ NH ₃ )Mo ₃ O ₁₀ got The resulting solution obtained by dissolving 1.799 g of (C ₂ H ₅ NH ₃ )Mo ₃ O ₁₀ in 20 g of pure water was mixed with a solution obtained by adding 0.658 g of vanadyl sulfate to 20 g of pure water, stirring at room temperature, and stirring for 10 minutes. . Subsequently, 0.327 g of bismuth oxychloride was added and stirred for further 10 minutes, and 2M sulfuric acid was added to adjust the pH to 2.0. The obtained mixed solution was transferred to a Teflon autoclave in which a Teflon sheet was previously inserted, and bubbling was performed with nitrogen at a flow rate of 50 L/min for 10 minutes. Thereafter, while rotating the autoclave at 1 rpm, solid content was produced using a hydrothermal method in an oven at 175°C for 48 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was mixed with 20 mL of 1.2 M hydrochloric acid with respect to 1.0 g of solid content, followed by dispersion mixing at room temperature for 30 minutes. Thereafter, while washing well with 1000 g of pure water, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are each bonded by sharing oxygen at adjacent vertices. . In addition, it was confirmed that the metal oxide satisfies the above formula (II). Table 1 shows the mass ratio M2/M1 of the inert component, the molar ratio excluding oxygen, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 6]

(CH ₃ NH ₃ ) ₆ Mo ₇ O ₂₄ was obtained by adding 21.594 g of molybdenum trioxide to 33.2 mL of a 40% methylamine solution and completely dissolving it, followed by evaporation. To a solution obtained by dissolving 1.780 g of (CH ₃ NH ₃ ) ₆ Mo ₇ O ₂₄ in 20 g of pure water, 0.658 g of vanadyl sulfate was added to 20 g of pure water and stirred at room temperature. The resulting solution was mixed and stirred for 10 minutes. Subsequently, 0.156 g of copper sulfate pentahydrate was added and stirred for further 10 minutes. The pH at this time was 3.2. The obtained mixed solution was transferred to a Teflon autoclave in which a Teflon sheet was previously inserted, and bubbling was performed with nitrogen at a flow rate of 50 L/min for 10 minutes. Thereafter, while rotating the autoclave at 1 rpm, solid content was produced using a hydrothermal method in a 175°C oven for 20 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was mixed with 1.26 g of oxalic acid dihydrate and 25 g of pure water with respect to 1.0 g of solid content, followed by dispersion mixing at 60°C for 30 minutes. Thereafter, while washing well with 500 g of pure water, solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are each bonded by sharing oxygen at adjacent vertices. . In addition, it was confirmed that the metal oxide satisfies the above formula (II). Table 1 shows the mass ratio M2/M1 of the inactive component, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 7]

To a solution prepared by adding 28.04 g of distilled water to 28.04 mL of a 70% ethylamine solution, 21.594 g of molybdenum trioxide was added and completely dissolved, followed by evaporation to obtain (C ₂ H ₅ NH ₃ )Mo ₃ O got ₁₀ The resulting solution obtained by dissolving 1.799 g of (C ₂ H ₅ NH ₃ )Mo ₃ O ₁₀ in 20 g of pure water was mixed with a solution obtained by adding 0.658 g of vanadyl sulfate to 20 g of pure water, stirring at room temperature, and stirring for 10 minutes. . Subsequently, 0.161 g of ammonium metatungstate was added and stirred for further 10 minutes. The pH at this time was 2.4. The obtained mixed solution was transferred to a Teflon autoclave in which a Teflon sheet was previously inserted, and bubbling was performed with nitrogen at a flow rate of 50 L/min for 10 minutes. Thereafter, solid content was produced using a hydrothermal method in a 175°C oven for 48 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was mixed with 1.26 g of oxalic acid dihydrate and 25 g of pure water with respect to 1.0 g of solid content, followed by dispersion mixing at 60°C for 30 minutes. Thereafter, while washing well with 500 g of pure water, solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are each bonded by sharing oxygen at adjacent vertices. . In addition, it was confirmed that the metal oxide satisfies the above formula (II). Table 1 shows the mass ratio M2/M1 of the inactive component, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 8]

To a solution obtained by dissolving 1.780 g of (CH ₃ NH ₃ ) ₆ Mo ₇ O ₂₄ obtained in the same manner as in Production Example 6 in 20 g of pure water, 0.642 g of vanadyl sulfate was added to 20 g of pure water and stirred at room temperature to obtain a solution. Mix and stir for 10 minutes. Subsequently, 0.176 g of iron sulfate heptahydrate was added and the mixture was further stirred for 10 minutes. The pH at this time was 2.84. The obtained mixed solution was transferred to a Teflon autoclave and bubbled with nitrogen at a flow rate of 50 L/min for 10 minutes. Thereafter, while rotating the autoclave at 1 rpm, solid content was produced using a hydrothermal method in a 175°C oven for 20 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was mixed with 1.26 g of oxalic acid dihydrate and 25 g of pure water with respect to 1.0 g of solid content, followed by dispersion mixing at 60°C for 30 minutes. Thereafter, while washing well with 500 g of pure water, solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are each bonded by sharing oxygen at adjacent vertices. . In addition, it was confirmed that the metal oxide satisfies the above formula (II). For the corresponding metal oxide, the mass ratio M2/M1 of the inactive component and the difference spectrum by FT-IR measurement are shown in Table 1.

[Production Example 9]

The solid content after pulverization treatment obtained in the same manner as in Production Example 1 was calcined at 400 ° C. for 2 hours under air flow of 50 mL / min, and then fired at 550 ° C. for 2 hours under nitrogen flow of 50 mL / min. A metal oxide was obtained.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide did not have a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) were bonded by sharing oxygens at adjacent vertices. Table 1 also shows the mass ratio M2/M1 of the inactive component, the molar ratio excluding oxygen, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the metal oxide.

[Production Example 10]

A solution obtained by adding 1.766 g of ammonium heptamolybdate tetrahydrate to 120 g of pure water and stirring at room temperature was mixed with a solution obtained by adding 0.658 g of vanadyl sulfate to 20 g of pure water and stirring at room temperature, followed by stirring for 10 minutes. Subsequently, the pH was adjusted to 1.20 by adding 2M sulfuric acid. The obtained mixed solution was transferred to a Teflon autoclave and bubbled with nitrogen at a flow rate of 50 L/min for 10 minutes. After that, solid content was generated using a hydrothermal method in an oven at 175°C for 20 hours. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the pulverization treatment was calcined at 400°C for 2 hours under nitrogen flow at 50 mL/min to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. Further, X-ray diffraction measurement was performed, and the crystal structure was specified from the obtained X-ray diffraction pattern. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide did not have a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) were bonded by sharing oxygens at adjacent vertices. In addition, Table 1 shows the mass ratio M2/M1 of the inactive component, the molar ratio excluding oxygen, and the difference spectrum by FT-IR measurement for the metal oxide.

[Production Example 11]

A solution obtained by adding 1.766 g of ammonium heptamolybdate tetrahydrate to 20 g of pure water and stirring at room temperature was mixed with a solution obtained by adding 0.159 g of ammonium metavanadate to 20 g of pure water and stirring at room temperature, and stirring for 10 minutes. did. The pH of the obtained solution was 2.21. About the obtained solution after mixing, the obtained solid content was collect|recovered by performing evaporation, and it dried in 80 degreeC oven and removed the water|moisture content.

Then, the obtained solid content after drying was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method and the molar ratio of each element was calculated by ICP emission spectrometry. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide did not have a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) were bonded by sharing oxygens at adjacent vertices. In addition, as a result of performing X-ray diffraction measurement and performing crystal structure analysis from the obtained X-ray diffraction pattern, the obtained metal oxide is at least three kinds of MoO ₃ , (V _0.12 Mo _0.88 ) O _2.94 , V _0.95 Mo _0.97 O ₅ . It was found to be a mixture containing the compound. Table 1 shows the mass ratio M2/M1 of the inactive component, the molar ratio excluding oxygen, and the difference spectrum by FT-IR measurement for the corresponding metal oxide.

[Production Example 12]

5.30 g of ammonium heptamolybdate tetrahydrate was added to 30 g of pure water and stirred at room temperature. To a solution obtained, 1.40 g of antimony sulfate was added and stirred for 15 minutes. Subsequently, 2.35 g of vanadyl sulfate was added to 20 g of pure water, stirred at room temperature, and the obtained solution was mixed and stirred for 5 minutes. The pH at this time was 1.80. The obtained mixed solution was transferred to a Teflon autoclave, and solid content was generated using a hydrothermal method in an oven at 175°C for 24 hours while rotating the autoclave at 1 rpm. Thereafter, the solid content was collected by suction filtration, and dried in an oven at 80°C to remove moisture.

Then, the obtained solid content after drying was pulverized for 5 minutes using an agate mortar. With respect to the obtained solid content after the pulverization treatment, the average length and average aspect ratio of the crystals were measured. The results are shown in Table 1.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygens at adjacent vertices. It became. In addition, it was confirmed that the metal oxide satisfies the above formula (II). Table 1 shows the mass ratio M2/M1 of the inactive component, the difference spectrum by FT-IR measurement, and the BET specific surface area S for the corresponding metal oxide.

[Production Example 13]

The dried solid content obtained by the same method as in Production Example 1 was pulverized for 5 minutes using an agate mortar. With respect to the obtained solid content after the pulverization treatment, the average length and average aspect ratio of the crystals were measured. The results are shown in Table 1.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygens at adjacent vertices. It became. In addition, it was confirmed that the metal oxide satisfies the above formula (II). For the corresponding metal oxide, the mass ratio M2/M1 of the inactive component and the difference spectrum by FT-IR measurement are shown in Table 1.

[Production Example 14]

The solid content after drying obtained by the method similar to manufacture example 1 was baked by the method similar to manufacture example 1, and the metal oxide was obtained.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygens at adjacent vertices. It became. In addition, it was confirmed that the metal oxide satisfies the above formula (II). For the corresponding metal oxide, the mass ratio M2/M1 of the inactive component and the difference spectrum by FT-IR measurement are shown in Table 1.

[Production Example 15]

A solution obtained by adding 1.766 g of ammonium heptamolybdate tetrahydrate to 20 g of pure water and stirring at room temperature was mixed with a solution obtained by adding 0.642 g of vanadyl sulfate to 20 g of pure water and stirring at room temperature, followed by stirring for 10 minutes. The pH at this time was 3.16. About the obtained solution after mixing, the obtained solid content was collect|recovered by performing evaporation, and it dried in 80 degreeC oven and removed the water|moisture content.

Then, the obtained solid content after drying was pulverized for 5 minutes using an agate mortar.

Subsequently, the solid content after the grinding treatment was calcined by the same method as in Production Example 1 to obtain a metal oxide.

With respect to the obtained metal oxide, the pore diameter was measured by the molecular probe method. In addition, the crystal structure was identified by X-ray diffraction measurement and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide satisfies the above formula (I) and has a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygens at adjacent vertices. It became. In addition, it was confirmed that the metal oxide had an amorphous structure that satisfied the above formula (II) and showed diffraction peaks only at 2θ = 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in the X-ray diffraction pattern. Table 1 shows the mass ratio M2/M1 of the inactive component, the molar ratio excluding oxygen, and the difference spectrum by FT-IR measurement for the corresponding metal oxide.

[Examples 1 to 6]

Using the metal oxide obtained in Production Example 1 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 2 shows the composition of the source gas, supply conditions, reaction temperature and reaction results.

[Examples 7 to 14]

Using the metal oxide obtained in Production Example 1 as a catalyst, 4.5 g of sea sand was mixed with 0.1 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 2 shows the composition of the source gas, supply conditions, reaction temperature and reaction results.

[Examples 15 to 17]

Using the metal oxide obtained in Production Example 2 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 2 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 18 to 20]

Using the metal oxide obtained in Production Example 3 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 2 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 21 to 23]

Using the metal oxide obtained in Production Example 4 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 2 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 24 to 28]

Using the metal oxide obtained in Production Example 5 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 3 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 29 to 32]

Using the metal oxide obtained in Production Example 6 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 3 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 33 to 37]

Using the metal oxide obtained in Production Example 7 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 3 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 38 to 40]

Using the metal oxide obtained in Production Example 8 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 3 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Comparative Examples 1 to 3]

Using the metal oxide obtained in Production Example 9 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 3 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Comparative Examples 4 to 6]

Using the metal oxide obtained in Production Example 10 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by supplying a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 3 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Comparative Examples 7 to 8]

Using the metal oxide obtained in Production Example 11 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 3 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 41 to 45]

Using the metal oxide obtained in Production Example 12 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 4 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 46 to 50]

Using the metal oxide obtained in Production Example 13 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 4 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 51 to 54]

Using the metal oxide obtained in Production Example 14 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 4 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 55 and 56]

Using the metal oxide obtained in Production Example 15 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 4 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Example 57]

Using the metal oxide obtained in Production Example 1 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 4 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Example 58]

Using the metal oxide obtained in Production Example 1 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, and nitrogen. Table 4 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

[Examples 59 to 60]

Using the metal oxide obtained in Production Example 2 as a catalyst, 4.5 g of sea sand was mixed with 0.5 g of the catalyst and charged into the reactor. Subsequently, the reaction was performed by passing a raw material gas composed of methacrolein, oxygen, water vapor, and nitrogen. Table 4 shows the composition of the source gas, supply conditions, reaction temperature, and reaction results.

As shown in Tables 1 to 4, in Examples 1 to 60 in which a metal oxide having a specific composition ratio containing at least molybdenum and containing a specific cyclic structure was used as a catalyst, methacrylic acid was obtained in high yield. got Further, from the X-ray diffraction peak, the metal oxides obtained in Production Examples 1, 2, 5, 6, 8, and 12 to 14 are orthorhombic, the metal oxides obtained in Production Examples 3 and 7 are trigonal, and the metal oxides obtained in Production Examples 4 and 15 Metal oxides have been characterized as having an amorphous structure.

On the other hand, in Comparative Examples 1 to 8 in which a metal oxide not containing the above cyclic structure was used as a catalyst, the methacrylic acid yield was lower than that of Examples.

In Production Example 2, a metal oxide was obtained without pulverizing the dried solid content having an average crystal length of 7.9 µm. That is, compared to Production Example 1, the metal oxide can be obtained by a simpler method, and furthermore, when such a metal oxide is used as a catalyst, the effect of improving the continuous operation time in the production of methacrylic acid is obtained as described above. can be expected This is also inferred from Examples 1 to 4, 57 and Examples 59 and 60, in which the metal oxide obtained in Production Example 1 and Production Example 2 was used as a catalyst and the reaction was performed with the same W/F and raw material gas composition. can do. From Examples 1 to 4 and 57 using the metal oxide obtained in Production Example 1 as a catalyst, when the reaction temperature becomes high, the methacrylic acid yield is greatly reduced, and in Example 57 in which the reaction temperature is 317.0 ° C., the methacrylic acid yield is It can be seen that it is reduced to 18.8%. In contrast, in Examples 59 and 60, in which the metal oxide obtained in Production Example 2 was used as a catalyst, the decrease in methacrylic acid yield was suppressed when the reaction temperature was high, and Example 59 in which the reaction temperature was 318.0 ° C. Also, it can be seen that a high methacrylic acid yield of 29.8% is maintained. Therefore, when the crystal average length in the solid content is within a specific range, it can be said that a specific cyclic structure can be stably maintained even at a high reaction temperature, and a catalyst advantageous for long-term continuous operation can be obtained by a simple method.

Claims (43)

A catalyst used when producing methacrylic acid by oxidation of methacrolein, wherein the catalyst comprises a metal oxide containing molybdenum, and the metal oxide satisfies the following conditions (a) and (b) As a catalyst for producing methacrylic acid having a cyclic structure,
(a) a cyclic structure satisfying the following formula (I);
(Sum of moles of Mo, V and X): (number of moles of O) = 7:35 (I)
(In formula (I), Mo, V and O represent molybdenum, vanadium and oxygen, respectively. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt represents at least one element selected from the group consisting of rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium.)
(b) a cyclic structure in which seven metal-oxygen octahedrons (octahedral structures) are bonded by sharing oxygens of adjacent vertices;
The metal oxide satisfies the following condition (c),
(c) a metal oxide having a composition represented by the following formula (II);
Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)
(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0.24≤c≤0.38, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)
A catalyst for producing methacrylic acid, wherein the metal oxide is a metal oxide having an orthorhombic, trigonal or amorphous crystal structure that satisfies the following condition (g):
(g) A metal oxide showing diffraction peaks at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays). According to claim 1,
A catalyst for producing methacrylic acid, wherein the metal oxide satisfies at least one selected from the following conditions (d) to (f).
(d) A metal oxide that satisfies the following formula (III) when the mass of the metal oxide is M1 and the mass of the inactive component contained in the metal oxide is M2.
0≤M2/M1<0.05 (III)
(e) Difference spectrum between the infrared absorption spectrum obtained by FT-IR measurement of the metal oxide and the infrared absorption spectrum obtained by FT-IR measurement after maintaining the metal oxide in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes The metal oxide having absorption peaks at 1557 ± 10 cm ^-1 , 1456 ± 10 cm ^-1 and 1374 ± 10 cm ^-1 .
(f) A metal oxide having a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60 m ² /g. According to claim 2,
A catalyst for producing methacrylic acid, in which the metal oxide satisfies the following condition (g1).
(g1) A metal oxide showing diffraction peaks only at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays). According to claim 2,
In the above condition (g), further 2θ = 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° Catalyst for producing methacrylic acid, exhibiting a diffraction peak at ±0.3 °. According to claim 2,
In the above condition (g), further 2θ = 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° Catalyst for producing methacrylic acid, exhibiting a diffraction peak at ±0.3 °. A method for producing the catalyst for producing methacrylic acid according to claim 1,
(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;
(2) Step of firing the solid content to obtain a metal oxide
Method for producing a catalyst for producing methacrylic acid comprising a. A method for producing the catalyst for producing methacrylic acid according to claim 4,
(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;
(1b) dispersing the solid content in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid content;
(2b) Step of firing the solid content obtained in (1b) to obtain a metal oxide
Method for producing a catalyst for producing methacrylic acid comprising a. A method for producing the catalyst for producing methacrylic acid according to claim 5,
(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;
(1b) dispersing the solid content in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid content;
(2b) Step of firing the solid content obtained in (1b) to obtain a metal oxide
Method for producing a catalyst for producing methacrylic acid comprising a. According to any one of claims 6 to 8,
Method for producing a catalyst for producing methacrylic acid, wherein the solid content satisfies the following conditions (h) and (i).
(h) Solid content with an average crystal length of 2 to 50 μm as observed with an electron microscope.
(i) A solid content having an average aspect ratio of 2 to 30 as observed by an electron microscope.
(However, average aspect ratio = (average length of crystals) / (average diameter of crystals).) A method for producing methacrylic acid, wherein methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid according to claim 1. A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is prepared by the method according to claim 6, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is prepared by the method according to claim 7, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is prepared by the method according to claim 8, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. According to any one of claims 10 to 13,
A method for producing methacrylic acid, wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas.
methacrolein:oxygen:water vapor:A=k:l:m:n (IV)
(In formula (IV), A represents nitrogen or helium. k to n represent the molar ratio of each gas, and when k + l + m + n = 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0≤m<45.) According to any one of claims 10 to 13,
A method for producing methacrylic acid in which a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500°C and the following formula (V) is satisfied.
15<W/F<550 (V)
(In formula (V), W represents the mass (g) of the metal oxide charged in the reactor, and F represents the supply amount (mol/h) of methacrolein per unit time.) According to any one of claims 10 to 13,
A method for producing methacrylic acid, wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500°C and the following formula (VI) is satisfied.
0.00002<F/(S×W)<0.008 (VI)
(In formula (VI), S represents the BET specific surface area (m ² /g) of the metal oxide calculated by nitrogen adsorption, W represents the mass (g) of the metal oxide charged in the reactor, and F is It represents the supply amount (mol/h) of methacrolein per unit time.) A method for producing a methacrylic acid ester comprising esterifying methacrylic acid produced by the method according to any one of claims 10 to 13. A method for producing a methacrylic acid ester comprising producing methacrylic acid by the method according to any one of claims 10 to 13 and esterifying the methacrylic acid. As a catalyst used when producing methacrylic acid by oxidation of methacrolein, a catalyst for producing methacrylic acid containing a metal oxide satisfying the following conditions (b') and (c),
(b') a metal oxide containing a cyclic structure in which each of seven metal-oxygen octahedra (octahedral structure) is bonded;
(c) a metal oxide having a composition represented by the following formula (II);
Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)
(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0.24≤c≤0.38, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)
The metal oxide has a cyclic structure that satisfies the following condition (a),
(a) a cyclic structure satisfying the following formula (I);
(Sum of moles of Mo, V and X): (number of moles of O) = 7:35 (I)
(In formula (I), Mo, V and O represent molybdenum, vanadium and oxygen, respectively. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt represents at least one element selected from the group consisting of rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium.)
A catalyst for producing methacrylic acid, wherein the metal oxide is a metal oxide having an orthorhombic, trigonal or amorphous crystal structure that satisfies the following condition (g):
(g) A metal oxide showing diffraction peaks at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays). According to claim 19,
A catalyst for producing methacrylic acid, wherein the metal oxide satisfies at least one selected from the following conditions (d) to (f).
(d) A metal oxide that satisfies the following formula (III) when the mass of the metal oxide is M1 and the mass of the inactive component contained in the metal oxide is M2.
0≤M2/M1<0.05 (III)
(e) Difference spectrum between the infrared absorption spectrum obtained by FT-IR measurement of the metal oxide and the infrared absorption spectrum obtained by FT-IR measurement after maintaining the metal oxide in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes The metal oxide having absorption peaks at 1557 ± 10 cm ^-1 , 1456 ± 10 cm ^-1 and 1374 ± 10 cm ^-1 .
(f) A metal oxide having a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60 m ² /g. 21. The method of claim 20,
A catalyst for producing methacrylic acid, in which the metal oxide satisfies the following condition (g1).
(g1) A metal oxide showing diffraction peaks only at 2θ = 22.1° ± 0.3° and 45.2° ± 0.3° in an X-ray diffraction pattern (using Cu-Kα rays). 21. The method of claim 20,
In the above condition (g), further 2θ = 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° Catalyst for producing methacrylic acid, exhibiting a diffraction peak at ±0.3 °. 21. The method of claim 20,
In the above condition (g), further 2θ = 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° Catalyst for producing methacrylic acid, exhibiting a diffraction peak at ±0.3 °. As a catalyst used when producing methacrylic acid by oxidation of methacrolein, a catalyst for producing methacrylic acid containing a metal oxide having an amorphous crystal structure and satisfying the following conditions (c) and (g1),
(c) a metal oxide having a composition represented by the following formula (II);
Mo ₁ V _c X _d Z _e (NH ₄ ) _f O _g (II)
(In formula (II), Mo, V, NH ₄ and O respectively represent molybdenum, vanadium, ammonium root and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese , at least one element selected from the group consisting of iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium c to g represent the molar ratio of each component, 0.24≤c≤0.38, 0≤d<0.5 , 0≤e≤0.1, 0≤f≤0.1, and g is the molar ratio of oxygen required to satisfy the valence of each component.)
(g1) a metal oxide showing diffraction peaks only at 2θ=22.1°±0.3° and 45.2°±0.3° in an X-ray diffraction pattern (using Cu-Kα rays);
The metal oxide has a cyclic structure that satisfies the following condition (a),
(a) a cyclic structure satisfying the following formula (I);
(Sum of moles of Mo, V and X): (number of moles of O) = 7:35 (I)
(In formula (I), Mo, V and O respectively represent molybdenum, vanadium and oxygen. X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt represents at least one element selected from the group consisting of rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium.)
A catalyst for producing methacrylic acid, in which the metal oxide satisfies the following condition (b').
(b') A metal oxide containing a cyclic structure in which each of seven metal-oxygen octahedra (octahedral structure) is bonded. A method for producing the catalyst for producing methacrylic acid according to claim 19,
(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;
(2) Step of firing the solid content to obtain a metal oxide
Method for producing a catalyst for producing methacrylic acid comprising a. A method for producing the catalyst for producing methacrylic acid according to claim 24,
(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;
(2) Step of firing the solid content to obtain a metal oxide
Method for producing a catalyst for producing methacrylic acid comprising a. A method for producing the catalyst for producing methacrylic acid according to claim 22,
(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;
(1b) dispersing the solid content in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid content;
(2b) Step of firing the solid content obtained in (1b) to obtain a metal oxide
Method for producing a catalyst for producing methacrylic acid comprising a. A method for producing the catalyst for producing methacrylic acid according to claim 23,
(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300° C. for 3 to 200 hours to produce a solid content;
(1b) dispersing the solid content in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid content;
(2b) Step of firing the solid content obtained in (1b) to obtain a metal oxide
Method for producing a catalyst for producing methacrylic acid comprising a. 29. The method of any one of claims 25 to 28,
Method for producing a catalyst for producing methacrylic acid, wherein the solid content satisfies the following conditions (h) and (i).
(h) Solid content with an average crystal length of 2 to 50 μm as observed with an electron microscope.
(i) A solid content having an average aspect ratio of 2 to 30 as observed by an electron microscope.
(However, average aspect ratio = (average length of crystals) / (average diameter of crystals).) A method for producing methacrylic acid, wherein methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid according to claim 19. A method for producing methacrylic acid, wherein methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid according to claim 24. A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is prepared by the method according to claim 25, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is produced by the method according to claim 26, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is prepared by the method according to claim 27, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is prepared by the method according to claim 28, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for producing methacrylic acid. 36. The method of any one of claims 30 to 35,
A method for producing methacrylic acid, wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas.
methacrolein:oxygen:water vapor:A=k:l:m:n (IV)
(In formula (IV), A represents nitrogen or helium. k to n represent the molar ratio of each gas, and when k + l + m + n = 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0≤m<45.) 36. The method of any one of claims 30 to 35,
A method for producing methacrylic acid in which a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500°C and the following formula (V) is satisfied.
15<W/F<550 (V)
(In formula (V), W represents the mass (g) of the metal oxide charged in the reactor, and F represents the supply amount (mol/h) of methacrolein per unit time.) 36. The method of any one of claims 30 to 35,
A method for producing methacrylic acid, wherein a raw material gas containing methacrolein is supplied so that the reaction temperature is 180 to 500°C and the following formula (VI) is satisfied.
0.00002<F/(S×W)<0.008 (VI)
(In formula (VI), S represents the BET specific surface area (m ² /g) of the metal oxide calculated by nitrogen adsorption, W represents the mass (g) of the metal oxide charged in the reactor, and F is It represents the supply amount (mol/h) of methacrolein per unit time.) A method for producing a methacrylic acid ester comprising esterifying methacrylic acid produced by the method according to any one of claims 30 to 35. A method for producing a methacrylic acid ester comprising producing methacrylic acid by the method according to any one of claims 30 to 35 and esterifying the methacrylic acid. delete delete delete