WO2018051840A1

WO2018051840A1 - Methacrylic acid production catalyst and method for producing same, and method for producing methacrylic acid and methacrylic acid ester

Info

Publication number: WO2018051840A1
Application number: PCT/JP2017/031885
Authority: WO
Inventors: 加藤　裕樹
Original assignee: 三菱ケミカル株式会社
Priority date: 2016-09-14
Filing date: 2017-09-05
Publication date: 2018-03-22
Also published as: SA519401149B1; JPWO2018051840A1; KR102216827B1; KR20190042095A; CN109641192A; SG11201900754XA; MY189907A; CN109641192B; JP6414343B2

Abstract

Provided is a methacrylic acid production catalyst that achieves a high methacrylic acid yield. The methacrylic acid production catalyst is used when producing methacrylic acid by subjecting methacrolein to vapor-phase contact oxidation using molecular oxygen, and contains a heteropoly acid salt at least containing phosphorus, molybdenum, and vanadium. In an X-ray diffraction pattern of the methacrylic acid production catalyst as measured using a Cu-Kα ray after the methacrylic acid production catalyst is allowed to stand for 12 hours in an environment in which the temperature and humidity are maintained at 30°C and 90%, the ratio (I₁/I₀) of the absolute value of the peak intensity I₁ of the (322) plane attributed to the cubic crystal structure of a proton-type heteropoly acid to the absolute value of the peak intensity I₀ of the (222) plane attributed to the cubic crystal structure of the heteropoly acid salt is 0.01-0.80.

Description

Catalyst for producing methacrylic acid, method for producing the 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 esters.

As a catalyst for producing methacrylic acid used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, a heteropolyacid catalyst containing molybdenum element and phosphorus element is known. Examples of such a heteropolyacid catalyst include a proton type heteropolyacid whose counter cation is a proton, and a heteropoly acid salt in which a part of the proton is substituted with a cation other than a proton. As the heteropolyacid salt, an alkali metal salt whose cation is an alkali metal ion and an ammonium salt whose cation is an ammonium ion are known. Proton heteropolyacids are water-soluble, but alkali metal salts of heteropolyacids are generally poorly soluble because of the large cation radii (Non-patent Document 1).

Patent Document 1 includes an acid salt of a Keggin type heteropolyacid containing phosphorus and molybdenum, and has a peak intensity of 3.24 to 3.26 面 with respect to a peak intensity of 3.38 to 3.41 面 in X-ray diffraction. A catalyst for the production of methacrylic acid is proposed, characterized in that the ratio is from 0.001 to 0.01.

JP 2005-131577 A

However, when the catalyst described in Patent Document 1 is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, the yield of methacrylic acid is not sufficient as an industrial catalyst, and Improvements are desired. An object of this invention is to provide the catalyst for methacrylic acid manufacture with a high methacrylic acid yield.

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

[1] A catalyst for producing methacrylic acid containing a heteropoly acid salt containing at least phosphorus, molybdenum and vanadium, which is used when producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, and having a temperature of 30 In the X-ray diffraction pattern using Cu—Kα ray of the catalyst for producing methacrylic acid left for 12 hours in an environment kept at 90 ° C. and humidity of 90%, the (222) plane is attributed to the cubic structure of the heteropolyacid salt. The ratio (I ₁ / I ₀ ) of the absolute value of the peak intensity I ₁ of the (322) plane due to the cubic structure of the proton type heteropolyacid to the absolute value of the peak intensity I ₀ of 0.01 is 0.01 or more and 0.00. The catalyst for methacrylic acid production which is 80 or less.

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

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

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

[5] The catalyst for producing methacrylic acid according to [4], including a step of mixing the dried product of the heteropolyacid salt-containing solution i and the dried product of the heteropolyacid salt-containing solution ii to obtain a catalyst precursor. Production method.

[6] The method includes the step of mixing the heteropolyacid salt-containing liquid i and the heteropolyacid salt-containing liquid ii to obtain a heteropolyacid salt-containing liquid iii and drying it to obtain a catalyst precursor. The manufacturing method of the catalyst for methacrylic acid manufacture of description.

[7] A dried product of either the heteropolyacid salt-containing liquid i or the heteropolyacid salt-containing liquid ii is mixed with another heteropolyacid salt-containing liquid to obtain a heteropolyacid salt-containing liquid iv, which is dried. The process for producing a catalyst for methacrylic acid production according to [4], comprising a step of obtaining a catalyst precursor.

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

1.5 ≦ AMi / Pi ≦ 3.0 (1)
4.0 ≦ NH ₄ ii / Pii ≦ 5.0 (2)
1.0 ≦ Pii / Pi ≦ 2.0 (3)
(In the formulas (1) to (3), AMi is the number of moles of alkali metal ions contained in the heteropolyacid-containing liquid i, Pi is the number of moles of phosphorus contained in the heteropolyacid-containing liquid i, and NH ₄ ii is the above-mentioned The number of moles of ammonium ions contained in the heteropolyacid-containing liquid ii, and Pii represents the number of moles of phosphorus contained in the heteropolyacid-containing liquid ii, respectively).

[9] A method for producing methacrylic acid, which comprises producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen in the presence of the catalyst for producing methacrylic acid according to any one of [1] to [3].

[10] A method for producing a methacrylic acid ester obtained by esterifying methacrylic acid produced by the method for producing methacrylic acid according to [9].

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

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

[Catalyst for methacrylic acid production]
The catalyst for producing methacrylic acid according to the present invention is a catalyst containing a heteropoly acid salt containing at least phosphorus, molybdenum and vanadium, which is used in producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen. . The Cu—Kα ray of the catalyst (hereinafter also referred to as pre-treatment) after being left for 12 hours in an environment maintained at a temperature of 30 ° C. and a humidity of 90% (hereinafter also referred to as pre-treatment) is used. In the observed X-ray diffraction pattern, the peak intensity I of the (322) plane due to the cubic structure of the proton type heteropolyacid relative to the absolute value of the peak intensity I ₀ of the (222) plane due to the cubic structure of the heteropolyacid salt the ratio of the _first absolute value _{_(I} 1 _/ I 0) _(hereinafter referred to as the peak intensity ratio _{_(I} 1 / I ₀₎₎ is 0.01 or more 0.80 or less.

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

_{_{_{_{Mo a P b V c Cu d}}}} A e E f G g O h (4)
In formula (4), Mo, P, V, Cu and O are element symbols indicating molybdenum, phosphorus, vanadium, copper and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten and boron. E is selected from the group consisting of iron, zinc, chromium, magnesium, calcium, strontium, tantalum, cobalt, nickel, manganese, barium, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, cerium and lanthanum At least one element is indicated. G represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium. a, b, c, d, e, f, g and h represent the atomic ratio of each element. When a = 12, b = 0.5 to 3, c = 0.01 to 3, d = 0. 01 to 2, e = 0.1 to 3, f = 0 to 3, g = 0.01 to 3, and h is an atomic ratio of oxygen necessary to satisfy the valence of each element. The elemental composition is a value calculated by analyzing a component in which the catalyst is dissolved in aqueous ammonia by ICP emission spectrometry.

In the present invention, when an X-ray diffraction pattern using Cu—Kα rays is measured for the pretreated catalyst after the pretreatment of the catalyst according to the present invention, the peak intensity ratio (I ₁ / I ₀ ) satisfies the range of 0.01 or more and 0.80 or less. When the peak intensity ratio (I ₁ / I ₀ ) is 0.01 or more, the adsorption site of methacrolein on the catalyst surface increases and the catalytic activity is improved. Further, when the peak intensity ratio (I ₁ / I ₀ ) is 0.80 or less, the progress of sequential oxidation of methacrylic acid can be suppressed. Therefore, when the catalyst according to the present invention is used for methacrylic acid production, methacrylic acid can be obtained in high yield. Moreover, it can be expected that a high yield of methacrylic acid can be maintained even when the catalyst is used for a long period of time by having the heteropolyacid salt and the proton type heteropolyacid in a predetermined ratio as in the present invention.

In the measurement of the X-ray diffraction pattern, first, a pretreatment is performed on the catalyst for producing methacrylic acid. The pretreatment is performed by leaving the catalyst at a temperature of 30 ° C. in an environment kept at 90% humidity for 12 hours. By performing the pretreatment, water molecules are hydrated in the heteropolyacid contained in the catalyst for producing methacrylic acid, and a cubic structure of the proton type heteropolyacid is formed. A diffraction pattern was obtained by X-ray diffraction (counter cathode Cu—Kα ray) of the pretreated catalyst that had been subjected to the pretreatment, and the peak intensity I ₀ of the (222) plane due to the cubic structure of the heteropolyacid salt was The ratio (I ₁ / I ₀ ) of the absolute value of the peak intensity I ₁ of the (322) plane due to the cubic structure of the proton type heteropolyacid to the absolute value is calculated.

For example, in the case of Cs ₄ PVMo ₁₁ O ₄₀ which is a heteropolyacid salt containing cesium as a cation, the peak of the (222) plane appears at a position of 2θ = 26.241 ° (Troemel, M., Inst. F. Anorganischem Chem). , Frankfurt, Germany., ICDD Grant-in-Aid, (1995)). In the case of H ₄ PVMo ₁₁ O ₄₀ · 32H ₂ O, which is a proton type heteropolyacid, the peak of the (322) plane appears at a position of 2θ = 26.801 ° (Troemel, M., Inst. F. Anorganischem Chem). , Frankfurt, Germany., ICDD Grant-in-Aid (1994)). In addition, the peak position does not always match when the polyatom of the heteropolyacid, the heteroatom is substituted with another element, or due to the difference in the number of equivalents of the cation of the heteropolyacid salt, but the surface position can be determined by looking at the peak pattern. Can be confirmed. In addition, when a plurality of salts exist as the heteropolyacid salt and a plurality of peak patterns can be confirmed, the sum of absolute values of the respective intensities of the (222) plane peaks resulting from the cubic structure of the heteropolyacid salt is I ₀ . To do. The same applies to the I _1. The X-ray diffraction pattern can be measured with an X-ray structure analyzer (trade name: X′Pert PRO MPD, manufactured by PANalytical).

The peak intensity ratio (I ₁ / I ₀ ) is 0.01 or more and 0.80 or less, and from the viewpoint of achieving a higher methacrylic acid yield, the lower limit is preferably 0.05 or more, more preferably 0.40 or more. Preferably, 0.50 or more is more preferable. The upper limit is preferably 0.75 or less, more preferably 0.73 or less, and even more preferably 0.70 or less.

[Method for producing catalyst for producing methacrylic acid]
Although the manufacturing method of the catalyst for methacrylic acid manufacture concerning this invention is not specifically limited, For example, it can manufacture by the following method. The method includes a step of dissolving or suspending at least a phosphorus raw material, a molybdenum raw material, and a vanadium raw material in a solvent to prepare a catalyst raw material liquid (hereinafter also referred to as a catalyst raw material liquid preparation step), and a cation raw material in the catalyst raw material liquid. Adding a heteropoly acid salt-containing liquid (hereinafter also referred to as a cation addition process), drying the heteropoly acid salt-containing liquid to obtain a catalyst precursor (hereinafter also referred to as a drying process), and the catalyst And a step of producing a catalyst for producing methacrylic acid by heat-treating the precursor (hereinafter also referred to as a heat treatment step). Here, a step of molding the catalyst precursor (hereinafter also referred to as a molding step) may be included before the heat treatment step. In particular, the method for producing a methacrylic acid production catalyst according to the present invention comprises a heteropoly acid salt-containing liquid i containing at least a phosphorus raw material and an alkali metal ion raw material, and a heteropoly acid salt containing liquid ii containing at least a phosphorus raw material and an ammonium ion raw material. It is preferable to include a step of using and drying to obtain a catalyst precursor.

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

The raw material compound of each element is not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halides, oxoacids, oxoacid salts, and the like of each element are used alone or in combination of two or more. be able to. For example, phosphoric acid, phosphorus pentoxide, ammonium phosphate, or the like can be used as the phosphorus raw material. As the molybdenum raw material, molybdenum trioxide, ammonium paramolybdate, molybdic acid, molybdenum chloride, or the like can be used. As the vanadium raw material, ammonium metavanadate, phosphovanadomolybdic acid, vanadium pentoxide, or the like can be used. These may use 1 type and may use 2 or more types together.

As the solvent for dissolving or suspending the raw material compound, water, ethyl alcohol, acetone or the like can be used. These may use 1 type and may use 2 or more types together. Among these, water is preferable as the solvent.

In this step, one type of catalyst raw material liquid may be prepared, or two or more types may be prepared. In particular, it is preferable that two or more catalyst raw material liquids are prepared and mixed before and after the drying step described later from the viewpoint of easily controlling the peak intensity ratio (I ₁ / I ₀ ) within the scope of the present invention.

(Cation addition process)
In this step, a cation raw material is added to the catalyst raw material liquid obtained in the catalyst raw material liquid preparation step to obtain a heteropolyacid salt-containing liquid.

Here, the cation is capable of forming a heteropoly acid salt having a cubic crystal structure, and alkali metal ions such as potassium, rubidium, cesium, and ammonium ions are particularly preferable. When the cation is an alkali metal ion, examples of the cation raw material include alkali metal carbonates, hydrogen carbonates, hydroxides, chloride salts, sulfates, nitrates, and the like. When the cation is an ammonium ion, examples of the cation raw material include ammonium bicarbonate, ammonium carbonate, ammonium nitrate, and aqueous ammonia. These can use 1 type and can also use 2 or more types together. In the catalyst raw material liquid preparation step, a cation may be contained in the catalyst raw material liquid by using an alkali metal salt or ammonium salt of each element as a raw material for each element. As a cation raw material, it is preferable to use both an alkali metal ion raw material and an ammonium ion raw material from the viewpoint of methacrylic acid yield.

When adding the cation raw material to the catalyst raw material liquid, it is preferable to add the catalyst raw material liquid with stirring. The temperature at which the cation raw material is added is preferably 1 to 100 ° C. Then, after adding all or part of the cation raw material, it is preferable to heat and stir at 90 to 150 ° C. for 1 to 10 hours.

By changing the amount of the cation raw material added in this step, the peak intensity ratio (I ₁ / I ₀ ) can be adjusted to 0.01 or more and 0.80 or less. Moreover, when preparing 2 or more types of the said catalyst raw material liquid in the said catalyst raw material liquid preparation process, a cation raw material can be added to at least 1 type of catalyst raw material liquid in this process, and a heteropolyacid salt containing liquid can be prepared. In particular, preparing the heteropoly acid salt-containing liquid i containing at least a phosphorus raw material and an alkali metal ion raw material and the heteropoly acid salt containing liquid ii containing at least a phosphorus raw material and an ammonium ion raw material results in the peak intensity ratio (I ₁ / I ₀ ) is preferable from the viewpoint of easy control. Further, it is more preferable that the heteropolyacid salt-containing liquids i and ii satisfy the following formulas (1) to (3) from the viewpoint of easy control of the peak intensity ratio (I ₁ / I ₀ ).

1.5 ≦ AMi / Pi ≦ 3.0 (1)
4.0 ≦ NH ₄ ii / Pii ≦ 5.0 (2)
1.0 ≦ Pii / Pi ≦ 2.0 (3)
In formulas (1) to (3), AMi is the number of moles of alkali metal ions contained in the heteropolyacid-containing liquid i, Pi is the number of moles of phosphorus element contained in the heteropolyacid-containing liquid i, and NH ₄ ii is the above-mentioned The number of moles of ammonium ions contained in the heteropolyacid-containing liquid ii, and Pii respectively represent the number of moles of phosphorus element contained in the heteropolyacid-containing liquid ii. In the formula (1), AMi / Pi represents the ratio of the number of moles of alkali metal ions to phosphorus element in the heteropolyacid-containing liquid i. The lower limit of AMi / Pi is preferably 1.7 or more, and the upper limit is preferably 2.8 or less, the lower limit is 1.9 or more, and the upper limit is more preferably 2.6 or less. In the formula _{(2), NH 4 ii /} Pii indicates the number of moles of ammonium ions to phosphorus element in the heteropoly acid-containing liquid ii. The lower limit of NH ₄ ii / Pii is preferably 4.1 or more, and the upper limit is preferably 4.9 or less, the lower limit is 4.2 or more, and the upper limit is more preferably 4.8 or less. In the formula (3), Pii / Pi represents a mixing ratio of the heteropolyacid-containing liquids i and ii. The lower limit of Pii / Pi is preferably 1.1 or more, and the upper limit is preferably 1.9 or less, the lower limit is 1.2 or more, and the upper limit is more preferably 1.8 or less.

As a method for adjusting the peak intensity ratio (I ₁ / I ₀ ), for example, the value of Pii / Pi is increased or decreased within a range where the heteropolyacid salt-containing liquids i and ii satisfy the formulas (1) to (3). The method of letting it be mentioned. Increasing Pii / Pi tends to increase the peak intensity ratio (I ₁ / I ₀ ), and decreasing Pii / Pi tends to decrease the peak intensity ratio (I ₁ / I ₀ ).

(Drying process)
In this step, the heteropolyacid salt-containing liquid obtained in the cation addition step is dried to obtain a catalyst precursor.

The conditions such as drying method and drying temperature are not particularly limited, and can be appropriately selected depending on the shape and size of the desired dried product. Examples of the drying method include a drying method using a box-type dryer, a drum drying method, an airflow drying method, an evaporation to dryness method, and a spray drying method. The drying temperature can be, for example, 120 to 500 ° C, the lower limit is preferably 140 ° C or higher, and the upper limit is preferably 400 ° C or lower. Drying can be performed until the heteropolyacid salt-containing liquid is dried.

The structure of the obtained catalyst precursor can be confirmed by measuring by infrared absorption analysis. The catalyst precursor preferably has a Keggin type heteropolyacid structure. When the catalyst precursor has a Keggin type heteropolyacid structure, the obtained infrared absorption spectrum has characteristic peaks around 1060, 960, 870, and 780 cm ⁻¹ .

In addition, when there are two or more kinds of heteropolyacid salt-containing liquids obtained in the cation addition step, these can be mixed before and after this step. That is, mixing may be performed in the state of the heteropoly acid salt-containing liquid before drying, or may be performed in the state of the catalyst precursor after drying. Moreover, after drying 1 or more types of heteropolyacid salt containing liquid, what mixed with the other heteropolyacid salt containing liquid may be dried again, and a catalyst precursor may be obtained. By mixing two or more kinds of heteropolyacid salt-containing liquids containing heteropolyacid salts having different atomic ratios or catalyst precursors, the peak intensity ratio (I ₁ / I ₀ ) in the resulting catalyst is within the scope of the present invention. It is preferable to control to methacrylic acid yield. In particular, a catalyst having a higher methacrylic acid yield can be obtained by mixing two or more kinds of catalyst precursors containing heteropolyacid salts having different atomic ratios.

When using the heteropolyacid salt-containing liquids i and ii, a catalyst precursor can be obtained by the drying. For example, the catalyst precursor can be obtained by mixing the dried product of the heteropolyacid salt-containing liquid i and the dried product of the heteropolyacid salt-containing liquid ii. Further, the heteropolyacid salt-containing liquid i and the heteropolyacid salt-containing liquid ii can be mixed to obtain a heteropolyacid salt-containing liquid iii, which can be dried to obtain a catalyst precursor. Also, the dried product of either the heteropolyacid salt-containing liquid i or the heteropolyacid salt-containing liquid ii is mixed with the other heteropolyacid salt-containing liquid to obtain a heteropolyacid salt-containing liquid iv, which is dried. Thus, a catalyst precursor can be obtained.

(Molding process)
Before the heat treatment step described later, the catalyst precursor obtained by the drying step may be molded. The molding method is not particularly limited, and a known dry or wet molding method can be applied. For example, tableting molding, press molding, extrusion molding, granulation molding and the like can be mentioned. The shape of the molded product is not particularly limited, and examples thereof include a columnar shape, a ring shape, and a spherical shape. In addition, it is preferable to form only the catalyst precursor without adding a carrier or a binder to the catalyst precursor at the time of molding. However, known additives such as graphite and talc, as well as known from organic and inorganic substances, if necessary. A binder may be added.

(Heat treatment process)
In this step, a catalyst for methacrylic acid production is produced by heat-treating the catalyst precursor obtained by the drying step or the molded product of the catalyst precursor obtained by the molding step (hereinafter collectively referred to as catalyst precursor). . For example, the catalyst precursor can be heat-treated under the flow of at least one of air and inert gas. Here, the inert gas refers to a gas that does not decrease the catalytic activity, and examples thereof include nitrogen, carbon dioxide, helium, and argon. These may use 1 type and may mix and use 2 or more types. The heat treatment is preferably performed under a flow of oxygen-containing gas such as air.

Although the shape of the heat treatment container is not particularly limited, it is preferable to use a tubular heat treatment container having a cross-sectional area of 2 square centimeters or more and 100 square centimeters or less. The heat treatment temperature is preferably 300 ° C. or higher and 700 ° C. or lower, the lower limit is 320 ° C. or higher, and the upper limit is more preferably 450 ° C. or lower.

The structure of the resulting catalyst for producing methacrylic acid can be confirmed by measuring by infrared absorption analysis. The methacrylic acid production catalyst preferably has a Keggin type heteropolyacid structure. When the methacrylic acid production catalyst has a Keggin type heteropolyacid structure, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 1060, 960, 870, and 780 cm ⁻¹ .

[Method for producing methacrylic acid]
In the method for producing methacrylic acid according to the present invention, methacrolein is vapor-phase contact oxidized with molecular oxygen in the presence of the catalyst for methacrylic acid production according to the present invention to produce methacrylic acid. According to this method, methacrylic acid can be produced with a high yield, and a high methacrylic acid yield can be maintained for a long period of time.

Specifically, methacrylic acid can be produced by bringing a raw material gas containing methacrolein and molecular oxygen into contact with the methacrylic acid production catalyst according to the present invention. This reaction can be carried out in a fixed bed. The catalyst layer may be one layer or two or more layers. The catalyst for producing methacrylic acid may contain other additives. The concentration of methacrolein in the raw material gas is not particularly limited, but is preferably 1 to 20% by volume, the lower limit is preferably 3% by volume or more, and the upper limit is more preferably 10% by volume or less. The methacrolein may contain a small amount of impurities such as a lower saturated aldehyde that do not substantially affect the present reaction. The concentration of molecular oxygen in the raw material gas is preferably 0.4 to 4.0 mol with respect to 1.0 mol of methacrolein, the lower limit is preferably 0.5 mol or more, and the upper limit is more preferably 3.0 mol or less. The molecular oxygen source is preferably air from the viewpoint of economy. If necessary, a gas or the like enriched with molecular oxygen by adding pure oxygen to air may be used.

The raw material gas may be obtained by diluting methacrolein and molecular oxygen with an inert gas such as nitrogen or carbon dioxide. Further, water vapor may be added to the source gas. By performing the reaction in the presence of water vapor, methacrylic acid can be obtained with higher selectivity. The concentration of water vapor in the raw material gas is preferably from 0.1 to 50.0% by volume, the lower limit is preferably 1.0% by volume or more, and the upper limit is more preferably 40.0% by volume or less. The contact time between the raw material gas and the catalyst for producing methacrylic acid is preferably 1.5 to 15.0 seconds, the lower limit is preferably 2.0 seconds or more, and the upper limit is more preferably 5.0 seconds or less. The reaction pressure is preferably 0.1 MPa (G) to 1.0 MPa (G). Note that (G) means a gauge pressure. The reaction temperature is preferably 200 to 450 ° C, the lower limit is preferably 250 ° C or higher, and the upper limit is more preferably 400 ° C or lower.

[Method for producing methacrylate ester]
In the method for producing a methacrylic acid ester according to the present invention, methacrylic acid produced by the method according to the present invention is esterified. According to this method, a methacrylic acid ester can be obtained using methacrylic acid obtained by gas phase catalytic oxidation of methacrolein. The alcohol to be reacted with methacrylic acid is not particularly limited, and examples thereof include methanol, ethanol, isopropanol, n-butanol, and isobutanol. Examples of the resulting methacrylic acid ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. The reaction can be carried out in the presence of an acidic catalyst such as a sulfonic acid type cation exchange resin. The reaction temperature is preferably 50 to 200 ° C.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. “Parts” in Examples and Comparative Examples means parts by mass. The X-ray diffraction pattern was measured with an X-ray structure analyzer (trade name: X'Pert PRO MPD, manufactured by PANalytical). The analysis of the raw material gas and the product was performed using gas chromatography. 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 formula.

Conversion rate of methacrolein (%) = (β / α) × 100
Methacrylic acid selectivity (%) = (γ / β) × 100
Methacrylic acid yield (%) = (γ / α) × 100
In the formula, α represents the number of carbons in the supplied methacrolein, β represents the number of carbons in the reacted methacrolein, and γ represents the number of carbons in the produced methacrylic acid.

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

The obtained catalyst precursor was molded, and the molded product was put in a cylindrical quartz glass baking container having an inner diameter of 3 cm. A catalyst for methacrylic acid production was prepared by heating at 10 ° C./h under air flow and calcining at 380 ° C. for 5 hours. This catalyst for producing methacrylic acid had a Keggin type heteropolyacid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.9 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. In addition, as a result of measuring an X-ray diffraction pattern using Cu—Kα rays for the pretreated catalyst after leaving the catalyst for 12 hours in an environment maintained at a temperature of 30 ° C. and a humidity of 90%, I ₀ Was 2θ = 26.1 °, I ₁ was confirmed at 2θ = 26.3 °, and the peak intensity ratio I ₁ / I ₀ was 0.43.

The obtained catalyst for producing methacrylic acid was filled in a reaction tube, and reacted at a reaction temperature of 300 ° C. through a raw material gas consisting of 5% by volume of methacrolein, 10% by volume of oxygen, 30% by volume of water vapor and 55% by volume of nitrogen. . The product was collected and analyzed by gas chromatography to calculate methacrylic acid yield and the like. The results are shown in Table 1.

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

Then, the catalyst for methacrylic acid manufacture was manufactured from the catalyst precursor by the method similar to Example 1, and methacrylic acid was manufactured using this catalyst. This catalyst for producing methacrylic acid had a Keggin type heteropolyacid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.8 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. Further, a pre-treated catalyst was prepared in the same manner as in Example 1. As a result of measuring an X-ray diffraction pattern using Cu—Kα rays for the pre-treated catalyst, I ₀ was 2θ = 26.1 °, I ₁ was confirmed at a position of 2θ = 26.5 °, and the peak intensity ratio I ₁ / I ₀ was 0.69. The results are shown in Table 1.

[Example 3]
In 200 parts of pure water, 50 parts of molybdenum trioxide, 3.8 parts of ammonium metavanadate, 3.3 parts of an 85 mass% phosphoric acid aqueous solution, and 3.5 parts of copper (II) nitrate trihydrate were dissolved. The mixture was heated to 95 ° C. while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 ° C. and stirring with a rotary blade stirrer, 13.0 parts of cesium bicarbonate dissolved in 20 parts of pure water was added and stirred for 15 minutes to precipitate the cesium salt of the heteropolyacid. Thus, a heteropolyacid salt-containing liquid i-2 was obtained. On the other hand, 70 parts of molybdenum trioxide, 5.3 parts of ammonium metavanadate, 4.7 parts of 85 mass% phosphoric acid aqueous solution, and 4.9 parts of copper (II) nitrate trihydrate were dissolved in 280 parts of pure water. . The mixture was heated to 95 ° C. while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 ° C. and stirring with a rotary blade stirrer, 6.8 parts of ammonium carbonate dissolved in 20 parts of pure water was added and stirred for 15 minutes to precipitate the ammonium salt of the heteropolyacid, A heteropolyacid salt-containing liquid ii-3 was obtained. The heteropolyacid salt-containing liquids i-2 and ii-3 are mixed, and the resulting heteropolyacid salt-containing liquid iii-1 is stirred for 15 minutes while being kept at 95 ° C., and then evaporated to dryness to obtain a catalyst precursor. Got.

Then, the catalyst for methacrylic acid manufacture was manufactured from the catalyst precursor by the method similar to Example 1, and methacrylic acid was manufactured using this catalyst. This catalyst for producing methacrylic acid had a Keggin type heteropolyacid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _1.0 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. Further, a pre-treated catalyst was prepared in the same manner as in Example 1. As a result of measuring an X-ray diffraction pattern using Cu—Kα ray for the pre-treated catalyst, I ₀ was 2θ = 26.2 °, I ₁ was confirmed at a position of 2θ = 26.5 °, and the peak intensity ratio I ₁ / I ₀ was 0.09. The results are shown in Table 1.

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

Then, the catalyst for methacrylic acid manufacture was manufactured from the catalyst precursor by the method similar to Example 1, and methacrylic acid was manufactured using this catalyst. This catalyst for producing methacrylic acid had a Keggin type heteropolyacid structure. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.6 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. Further, a pre-treated catalyst was prepared in the same manner as in Example 1. As a result of measuring an X-ray diffraction pattern using Cu—Kα rays for the pre-treated catalyst, I ₀ was 2θ = 26.1 °, I ₁ was confirmed at a position of 2θ = 26.5 °, and the peak intensity ratio I ₁ / I ₀ was 0.75. The results are shown in Table 1.

[Comparative Example 1]
In 400 parts of pure water, 100 parts of molybdenum trioxide, 7.5 parts of ammonium metavanadate, 6.7 parts of 85 mass% phosphoric acid aqueous solution, and 7.0 parts of copper (II) nitrate trihydrate were dissolved. The mixture was heated to 95 ° C. while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 ° C. and stirring with a rotary blade stirrer, 26.0 parts of cesium bicarbonate dissolved in 40 parts of pure water was added and stirred for 15 minutes to precipitate the cesium salt of the heteropolyacid. It was. The obtained heteropolyacid salt-containing liquid i-4 was evaporated to dryness to obtain a catalyst precursor.

Then, the catalyst for methacrylic acid manufacture was manufactured from the catalyst precursor by the method similar to Example 1, and methacrylic acid was manufactured using this catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _2.3 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. Further, a pre-treated catalyst was prepared in the same manner as in Example 1. As a result of measuring an X-ray diffraction pattern using Cu—Kα ray for the pre-treated catalyst, I ₀ was a position of 2θ = 26.0 °. Was confirmed. On the other hand, it was 0 for I ₁ could not be confirmed. Therefore, the peak intensity ratio I ₁ / I ₀ was 0.00. The results are shown in Table 1.

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

Then, the catalyst for methacrylic acid manufacture was manufactured from the catalyst precursor by the method similar to Example 1, and methacrylic acid was manufactured using this catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.7 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. Further, a pre-treated catalyst was prepared in the same manner as in Example 1. As a result of measuring an X-ray diffraction pattern using Cu—Kα rays for the pre-treated catalyst, I ₀ was 2θ = 26.1 °, I ₁ was confirmed at a position of 2θ = 26.5 °, and the peak intensity ratio I ₁ / I ₀ was 0.81. The results are shown in Table 1.

[Comparative Example 3]
A catalyst precursor A1 was obtained in the same manner as in Example 1. On the other hand, in 455.2 parts of pure water, 114 parts of molybdenum trioxide, 8.6 parts of ammonium metavanadate, 7.6 parts of 85% by weight aqueous phosphoric acid solution, and 8.0 parts of copper (II) nitrate trihydrate were added. Dissolved. The mixture was heated to 95 ° C. while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. While maintaining the liquid temperature at 95 ° C. and stirring with a rotary blade stirrer, 10.1 parts of ammonium carbonate dissolved in 42.1 parts of pure water was added and stirred for 15 minutes to precipitate the ammonium salt of the heteropolyacid. I let you. The obtained heteropolyacid salt-containing liquid ii-6 was evaporated to dryness to obtain a catalyst precursor B5. Next, the catalyst precursors A1 and B5 were mixed to obtain a catalyst precursor.

Then, the catalyst for methacrylic acid manufacture was manufactured from the catalyst precursor by the method similar to Example 1, and methacrylic acid was manufactured using this catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 Cs _0.5 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. Further, a pre-treated catalyst was prepared in the same manner as in Example 1. As a result of measuring an X-ray diffraction pattern using Cu—Kα ray for the pre-treated catalyst, I ₀ was 2θ = 26.2 °, I ₁ was confirmed at a position of 2θ = 26.4 °, and the peak intensity ratio I ₁ / I ₀ was 2.25. The results are shown in Table 1.

[Comparative Example 4]
In 400 parts of pure water, 100 parts of molybdenum trioxide, 7.5 parts of ammonium metavanadate, 6.7 parts of 85 mass% phosphoric acid aqueous solution, and 7.0 parts of copper (II) nitrate trihydrate were dissolved. The mixture was heated to 95 ° C. while stirring, and stirred for 2 hours while maintaining the liquid temperature at 95 ° C. The obtained heteropolyacid salt-containing liquid ii-7 was evaporated to dryness to obtain a catalyst precursor.

Then, the catalyst for methacrylic acid manufacture was manufactured from the catalyst precursor by the method similar to Example 1, and methacrylic acid was manufactured using this catalyst. The composition of the catalyst was Mo ₁₂ P _1.0 V _1.1 Cu _0.5 . The elemental composition was calculated by analyzing a component in which the catalyst was dissolved in aqueous ammonia by ICP emission spectrometry. Further, a pre-treated catalyst was prepared in the same manner as in Example 1. As a result of measuring an X-ray diffraction pattern using Cu—Kα ray for the pre-treated catalyst, I ₁ was a position of 2θ = 26.5 °. Was confirmed. On the other hand, since I ₀ was not observed, it was set to 0. Therefore, the peak intensity ratio I ₁ / I ₀ could not be calculated. The results are shown in Table 1.

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

On the other hand, in Comparative Examples 1 to 4, the peak intensity ratio (I ₁ / I ₀ ) was outside the specified range in the present invention, and the methacrylic acid yield was lower than in Examples 1 to 4. In Comparative Example 4, the peak pattern due to the heteropolyacid salt was not confirmed, and I ₀ was 0, so the peak intensity ratio (I ₁ / I ₀ ) could not be calculated. Even in such a case, the yield of methacrylic acid was low, and it was confirmed that the yield of methacrylic acid was low when the peak intensity ratio (I ₁ / I ₀ ) was outside the specified range in the present invention. In addition, a methacrylic acid ester can be obtained by esterifying the methacrylic acid obtained in the present Example.

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

As mentioned above, although this invention was demonstrated with reference to embodiment and an Example, this invention is not limited to the said embodiment and Example. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

The catalyst for producing methacrylic acid according to the present invention is industrially useful because it shows a high yield of methacrylic acid when it is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen. . In addition, since the crystal structure of the heteropoly acid salt and the proton type heteropoly acid is used as described above, the proton type heteropoly acid effectively functions as an active site while maintaining the stability of the heteropoly acid salt, which is high for a long period of time. It can be expected that the yield of methacrylic acid is expressed.

Claims

A catalyst for producing methacrylic acid containing a heteropolyacid salt containing at least phosphorus, molybdenum and vanadium, which is used when producing methacrolein by vapor phase catalytic oxidation of methacrolein with molecular oxygen, temperature 30 ° C., humidity In the X-ray diffraction pattern using the Cu—Kα ray of the catalyst for producing methacrylic acid left for 12 hours in an environment maintained at 90%, the peak intensity of the (222) plane due to the cubic structure of the heteropolyacid salt with respect to the absolute value of I 0, due to the cubic structure of the proton-type heteropoly acid (322) plane ratio of the absolute value of the peak intensity I 1 of (I 1 / I 0) is 0.01 or more 0.80 or less A catalyst for producing methacrylic acid.
The catalyst for producing methacrylic acid according to claim 1, wherein I 1 / I 0 is 0.05 or more and 0.75 or less.
The catalyst for methacrylic acid production according to claim 2, wherein I 1 / I 0 is 0.40 or more and 0.73 or less.
A method for producing a catalyst for methacrylic acid production according to any one of claims 1 to 3, wherein at least a phosphorus raw material and a heteropoly acid salt-containing liquid i containing an alkali metal ion raw material, and at least a phosphorus raw material and ammonium ion The manufacturing method of the catalyst for methacrylic acid manufacture including the process of obtaining the catalyst precursor by drying using the heteropolyacid salt containing liquid ii containing a raw material.
The method for producing a catalyst for methacrylic acid production according to claim 4, comprising a step of mixing the dried product of the heteropolyacid salt-containing solution i and the dried product of the heteropolyacid salt-containing solution ii to obtain a catalyst precursor.
The methacrylic acid of Claim 4 including the process of mixing the said heteropolyacid salt containing liquid i and the said heteropolyacid salt containing liquid ii, obtaining heteropolyacid salt containing liquid iii, and drying this to obtain a catalyst precursor. A method for producing a catalyst for acid production.
One of the heteropolyacid salt-containing liquid i and the heteropolyacid salt-containing liquid ii is mixed with the other heteropolyacid salt-containing liquid to obtain a heteropolyacid salt-containing liquid iv, which is dried to obtain a catalyst. The manufacturing method of the catalyst for methacrylic acid manufacture of Claim 4 including the process of obtaining a precursor.
The method for producing a catalyst for methacrylic acid production according to any one of claims 4 to 7, wherein the heteropolyacid salt-containing liquids i and ii satisfy the following formulas (1) to (3).
1.5 ≦ AMi / Pi ≦ 3.0 (1)
4.0 ≦ NH 4 ii / Pii ≦ 5.0 (2)
1.0 ≦ Pii / Pi ≦ 2.0 (3)
(In the formulas (1) to (3), AMi is the number of moles of alkali metal ions contained in the heteropolyacid-containing liquid i, Pi is the number of moles of phosphorus contained in the heteropolyacid-containing liquid i, and NH 4 ii is the above-mentioned (The number of moles of ammonium ions contained in the heteropolyacid-containing liquid ii, Pii represents the number of moles of phosphorus contained in the heteropolyacid-containing liquid ii, respectively.)
A method for producing methacrylic acid, wherein methacrylic acid is produced by gas-phase catalytic oxidation of methacrolein with molecular oxygen in the presence of the catalyst for producing methacrylic acid according to any one of claims 1 to 3.
A method for producing a methacrylic acid ester, wherein the methacrylic acid produced by the method for producing methacrylic acid according to claim 9 is esterified.
The manufacturing method of the methacrylic acid ester which manufactures methacrylic acid by the method of Claim 9, and esterifies this methacrylic acid.