Catalyst for methacrylic acid production, method for producing same, and method for producing methacrylic acid and methacrylic acid esters using catalyst

Abstract

The present invention addresses the problems of providing a catalyst that has high heat resistance and that enables methacyrlic acid to be produced at high yield, and providing a method for producing methacyrlic acid and methacrylic acid esters using the catalyst. The above problems are solved by using a catalyst having a specific 31P-NMR spectrum.

Description

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

[0001] 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 using the same.

[0002] Known examples of catalysts for producing methacrylic acid (hereinafter also simply referred to as "catalysts") used in producing methacrylic acid by oxidizing methacrolein include heteropolyacid catalysts containing molybdenum and phosphorus. Heteropolyacids are condensed oxygen acids formed by 12 coordination atoms (hereinafter referred to as "polyatoms") that form the basic skeleton of a polyacid and oxides of the heteroatoms. Examples of heteropolyacid catalysts include proton-type heteropolyacids in which the counter cation is a proton, and heteropolyacid salts in which some of the protons are replaced with cations other than protons (hereinafter, proton-type heteropolyacids will be simply referred to as "heteropolyacids," and at least one selected from proton-type heteropolyacids and heteropolyacid salts will be simply referred to as "heteropolyacids (salts)").

[0003] Regarding the structure of heteropolyacids (salts), Non-Patent Document 1 describes that phosphorus, silicon, arsenic, germanium, titanium, antimony, etc. can be heteroatoms, and tungsten, molybdenum, vanadium, niobium, tantalum, etc. can be polyatoms of heteropolyacids (salts). Furthermore, the basic structures of heteropolyacids (salts) include Keggin type, Dawson type, Preysler type, etc.

[0004] Furthermore, Patent Document 1 discloses a catalyst for producing methacrylic acid, which is made of a Keggin-type heteropolyacid salt having a composition represented by the following formula: P ａ Mo ｂ V ｃ X ｄ Y ｅ O ｆ(In the formula, P, Mo, V, and O represent phosphorus, molybdenum, vanadium, and oxygen, respectively; X represents at least one element selected from potassium, rubidium, cesium, and thallium; Y represents at least one element selected from copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, and cerium; a, b, c, d, e, and f represent atomic ratios of P, Mo, V, X, Y, and O, respectively, where, when b=12, a, c, d, and e each independently represent a value exceeding 0 and not exceeding 3; and f is a value determined by the oxidation state and atomic ratio of each element other than oxygen.)

[0005] Keggin type heteropolyacids include H ３ PMo １２ O ４０ , H ４ PMo １１ VO ４０ H ３ , P.W. １２ O ４０ etc. are known, and Non-Patent Document 1 states that H ３ PMo １２ O ４０ and H ４ PMo １１ VO ４０ H ３ Compared to P.W. １２ O ４０ On the other hand, Non-Patent Document 2 discloses that H is used as a catalyst for producing methacrylic acid. ３ PMo １２ O ４０ When PW is used, methacrylic acid is easily obtained. １２ O ４０ It has been described that when the above-mentioned hydroxylase is used, both the activity and the selectivity are very low.

[0006] Japanese Patent Application Laid-Open No. 2003-010691

[0007] Toshio Okuhara, Noritaka Mizuno, Makoto Misono, Advances in Catalysis, volume 41. Shuhei Yasuda, Atsuki Iwakura, Jun Hirata, Mitsuru Kanno, Wataru Ninomiya, Ryoichi Otomo, Yuichi Kamiya, Catalysis Communications, 125 (2019), 43-47.

[0008] However, known catalysts for producing methacrylic acid have low heat resistance and still insufficient catalytic life. Therefore, for use as an industrial catalyst, there is a need for the development of a catalyst that is highly heat resistant and capable of producing methacrylic acid in a high yield. An object of the present invention is to provide a catalyst that is highly heat resistant and capable of producing methacrylic acid in a high yield. Another object of the present invention is to provide a method for producing methacrylic acid and methacrylic acid esters using this catalyst.

[0009] As a result of intensive research in view of the above problems, the present inventors have found that ３１ The present invention has been completed based on the discovery that the above-mentioned problems can be solved by using a catalyst having a P-NMR spectrum. That is, the present invention includes the following: [1]: A catalyst used in producing methacrylic acid by oxidation of methacrolein, the catalyst containing a heteropolyacid containing phosphorus, molybdenum, and tungsten, ３１ A catalyst for producing methacrylic acid, wherein, in a P-NMR spectrum, the area of ​​a signal observed in the range of -5.2 ppm or more to less than 0 ppm is defined as A, the area of ​​a signal observed in the range of -10 ppm or more to less than -5.2 ppm is defined as B, and the area of ​​a signal observed in the range of -20 ppm or more to less than -10 ppm is defined as C, and C / (A+B+C) is 0.015 to 0.085. [2]: The catalyst for producing methacrylic acid, ３１ The catalyst for producing methacrylic acid according to [1], wherein B / (A+B+C) is 0.1 to 0.485 in a P-NMR spectrum. ３１The catalyst for producing methacrylic acid according to [1] or [2], wherein A / (A+B+C) is 0.5 to 0.885 in a P-NMR spectrum. ３１ The catalyst for producing methacrylic acid according to any one of [1] to [3], wherein in a P-NMR spectrum, C / (A+B+C) is 0.02 to 0.08. ３１ The catalyst for producing methacrylic acid according to any one of [1] to [4], wherein in a P-NMR spectrum, B / (A+B+C) is 0.2 to 0.045. ３１ The catalyst for producing methacrylic acid according to any one of [1] to [5], wherein A / (A+B+C) is 0.53 to 0.75 in a P-NMR spectrum. [7]: The catalyst for producing methacrylic acid according to any one of [1] to [6], which has a composition represented by the following formula (I): P ａ Mo ｂ W ｃ V ｄ Cu ｅ A ｆ E ｇ G ｈ O ｉ(I) In formula (I), P, Mo, W, V, Cu, and O represent phosphorus, molybdenum, tungsten, vanadium, copper, and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, tellurium, selenium, and silicon. E represents at least one element selected from the group consisting of iron, zinc, chromium, tantalum, cobalt, nickel, manganese, titanium, and niobium. G represents at least one element selected from the group consisting of potassium, rubidium, and cesium. a to i represent the molar ratios of each component, where b + c = 12, a = 0.5 to 3, c = 0.22 to 5, d = 0.01 to 3, e = 0.01 to 2, f = 0 to 3, g = 0 to 3, and h = 0.01 to 3, and i represents the molar ratio of oxygen required to satisfy the valence of each component. [8]: The catalyst for producing methacrylic acid according to [7], wherein in formula (I), c = 0.22 to 3. [9]: A method for producing the catalyst for producing methacrylic acid according to any one of [1] to [8], comprising the steps of: (i) mixing a phosphorus raw material, a molybdenum raw material, and a tungsten raw material with a solvent to prepare a solution or slurry (liquid A) having a pH of 0.1 to 4, (ii) drying said liquid A to obtain a dried product, and (iii) calcining said dried product to obtain a calcined product.

[10] : The method for producing the catalyst for producing methacrylic acid according to [9], wherein in the step (i), the tungsten raw material having a solubility in water at 20°C of 4.1 g / 100 mL or more accounts for 50 mass% or more of the total tungsten raw material.

[11] : A method for producing a catalyst for producing methacrylic acid according to [9] or

[10] , wherein in the step (i), the pH of the solution A is 0.1 to 3.

[12] : A method for producing methacrylic acid, comprising a step of producing methacrylic acid by oxidizing methacrolein using the catalyst for producing methacrylic acid according to any one of [1] to [8].

[13] : A method for producing methacrylic acid, comprising a step of producing methacrylic acid by oxidizing methacrolein using the catalyst for producing methacrylic acid produced by the method according to any one of [9] to

[12] .

[14] : A method for producing a methacrylic acid ester, comprising a step of esterifying methacrylic acid produced by the method according to

[12] or

[13] .

[0010] According to the present invention, it is possible to provide a catalyst which has high heat resistance and can produce methacrylic acid in a high yield.

[0011] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits, and "A to B" means A or more and B or less.

[0012] [Catalyst for producing methacrylic acid] The catalyst for producing methacrylic acid according to this embodiment is a catalyst used when producing methacrylic acid by oxidation of methacrolein, and contains a heteropolyacid containing phosphorus, molybdenum, and tungsten. ３１ In the P-NMR spectrum, when the area of ​​the signal observed in the range of -5.2 ppm or more and less than 0 ppm is A, the area of ​​the signal observed in the range of -10 ppm or more and less than -5.2 ppm is B, and the area of ​​the signal observed in the range of -20 ppm or more and less than -10 ppm is C, C / (A+B+C) is 0.015 to 0.085. Such a catalyst has high heat resistance and can produce methacrylic acid in a high yield.

[0013] <Catalyst ３１ P-NMR spectrum of catalyst ３１In the P-NMR spectrum, A, B, and C are the areas of signals primarily attributable to the Keggin-type heteropolyacid structure. Specifically, A is the area of ​​signals primarily attributable to a structure in which the heteroatom is primarily phosphorus and the polyatom is molybdenum (hereinafter also referred to as Structure A). B is the area of ​​signals primarily attributable to a structure in which the heteroatom is primarily phosphorus, 1 to 5 of the polyatoms are atoms such as tungsten or vanadium, and the remainder is molybdenum (hereinafter also referred to as Structure B). C is the area of ​​signals primarily attributable to a structure in which the heteroatom is primarily phosphorus, 6 to 12 of the polyatoms are atoms such as tungsten or vanadium, and the remainder is molybdenum (hereinafter also referred to as Structure C). The catalyst containing Structure A and Structure B exhibits a good yield in the production of methacrylic acid. On the other hand, when Structure A is present in excess, the yield tends to decrease due to the promotion of successive oxidation reactions of methacrylic acid. Furthermore, Structures B and C have higher thermal decomposition temperatures and superior heat resistance compared to Structure A. Structure C, in which most of the polyatoms are atoms such as W and V, is particularly excellent in heat resistance.

[0014] The catalyst for producing methacrylic acid according to this embodiment ３１In the P-NMR spectrum, C / (A+B+C) is 0.015 to 0.085. At this time, Structure A and Structure B, which exhibit good yields in the production of methacrylic acid, and Structure C, which is particularly excellent in heat resistance, are present in a suitable ratio in the catalyst. Therefore, it is believed that a catalyst with high heat resistance and excellent methacrylic acid yield can be obtained. The lower limit of C / (A+B+C) is preferably 0.02 or more, more preferably 0.025 or more. The upper limit of C / (A+B+C) is preferably 0.08 or less, more preferably 0.75 or less. B / (A+B+C) is preferably 0.1 or more. At this time, Structure B, which exhibits both excellent yields and heat resistance in the production of methacrylic acid, is present in an appropriate amount in the catalyst, resulting in a catalyst with better heat resistance and methacrylic acid yield. B / (A+B+C) is more preferably 0.2 or more. The upper limit of B / (A+B+C) is preferably 0.985 or less, more preferably 0.98 or less, even more preferably 0.485 or less, and particularly preferably 0.45 or less. The lower limit of A / (A+B+C) is preferably 0.5 or more, more preferably 0.53 or more, and even more preferably 0.56 or more, from the viewpoint of methacrylic acid yield. The upper limit of A / (A+B+C) is preferably 0.885 or less, more preferably 0.78 or less, and particularly preferably 0.75 or less, from the viewpoint of suppressing the successive oxidation of methacrylic acid. The preferred upper and lower limits of C / (A+B+C), B / (A+B+C) and A / (A+B+C) can be selected in any combination, for example, C / (A+B+C) may be 0.015 to 0.085, B / (A+B+C) may be 0.1 to 0.985, and A / (A+B+C) may be 0 to 0.885, or C / (A+B+C) may be 0.015 to 0.085, B / (A+B+C) may be 0.1 to 0.485, and A / (A+B+C) may be 0.5 to 0. 885, C / (A+B+C) may be 0.02 to 0.08, B / (A+B+C) may be 0 to 0.98, A / (A+B+C) may be 0 to 0.98, C / (A+B+C) may be 0.02 to 0.08, B / (A+B+C) may be 0.2 to 0.98, A / (A+B+C) may be 0 to 0.78, C / (A+B+C) may be 0.02 to 0.08, B / (A+B+C) may be 0.2 to 0.45, A / (A+B+C) may be 0.53 to 0.75.

[0015] ​３１ Examples of methods for obtaining a catalyst having C / (A+B+C) and A / (A+B+C) within specified ranges in the P-NMR spectrum include a method of producing a catalyst by a method including steps (i) to (iii) described below, and adjusting the amount of the tungsten raw material used in step (i) and the pH of the resulting Solution A, and a method of adjusting the calcination temperature and time in step (iii).

[0016] In addition ３１ P-NMR spectra are obtained by filling a sample tube with 300 mg of powdered catalyst and measuring at room temperature using an apparatus such as an AVANCE 300 (manufactured by Bruker). A 7 mm MAS probe is used for the measurement, and the measurement conditions are a resonance frequency of 121.4 MHz, a pulse width of 5.5 μs, a signal acquisition time of 0.066 s, an accumulation count of 64, a repeat waiting time of 150 s, and an MAS rotation speed of 5000 Hz. The horizontal axis represents the chemical shift (ppm), and the vertical axis represents the detection signal. ３１ In the P-NMR spectrum, the absolute values ​​of the areas calculated by quadrature analysis for signals observed in the ranges of −5.2 ppm or more and less than 0 ppm, −10 ppm or more and less than −5.2 ppm, and −20 ppm or more and less than −10 ppm are designated as A, B, and C, respectively. The horizontal axis is set to the chemical shift of an 85% aqueous phosphoric acid solution as 0 ppm.

[0017] <Catalyst Composition> From the viewpoint of methacrylic acid yield, the catalyst for producing methacrylic acid according to this embodiment preferably has a composition represented by the following formula (I). The catalyst may contain small amounts of elements not represented by the following formula (I). ａ Mo ｂ W ｃ V ｄ Cu ｅ A ｆ E ｇ G ｈ O ｉ(I) In formula (I), P, Mo, W, V, Cu, and O represent phosphorus, molybdenum, tungsten, vanadium, copper, and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, tellurium, selenium, and silicon. E represents at least one element selected from the group consisting of iron, zinc, chromium, tantalum, cobalt, nickel, manganese, titanium, and niobium. G represents at least one element selected from the group consisting of potassium, rubidium, and cesium. a to i represent the molar ratios of each component, where b + c = 12, a = 0.5 to 3, c = 0.22 to 5, d = 0.01 to 3, e = 0.01 to 2, f = 0 to 3, g = 0 to 3, and h = 0.01 to 3, and i represents the molar ratio of oxygen required to satisfy the valence of each component.

[0018] In the formula (I), the molar ratio c of W (tungsten) satisfies c = 0.22 to 5. This allows for the formation of a structure C with particularly excellent heat resistance. The lower limit of c is preferably 0.23 or more, and more preferably 0.3 or more. The upper limit of c is preferably 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.8 or less.

[0019] In addition, in the formula (I), from the viewpoint of improving the yield of methacrylic acid, the lower limit of a is preferably 0.6 or more, more preferably 0.7 or more. The upper limit of a is preferably 2.5 or less, more preferably 2 or less. The lower limit of d is preferably 0.1 or more, preferably 0.15 or more, more preferably 0.2 or more. The upper limit of d is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.5 or less. The lower limit of e is preferably 0.03 or more, more preferably 0.05 or more. The upper limit of e is preferably 2.5 or less, more preferably 2 or less. The lower limit of f is preferably 0.01 or more, more preferably 0.1 or more. The upper limit of f is preferably 2.5 or less, more preferably 2 or less. The upper limit of g is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1 or less. The lower limit of h is preferably 0.1 or more, more preferably 0.3 or more. The upper limit of h is preferably 2.8 or less, more preferably 2.5 or less.

[0020] The molar ratio of each component is determined by dissolving the catalyst in aqueous ammonia and analyzing the resulting solution by ICP emission spectrometry.

[0021] [Method for producing a catalyst for producing methacrylic acid] The catalyst for producing methacrylic acid according to this embodiment is ３１ If the above-mentioned C / (A+B+C) is 0.015 to 0.085 in the P-NMR spectrum, the catalyst can be produced in accordance with known catalyst production methods, but it is preferably produced by a method including the following steps (i) to (iii): (i) mixing a phosphorus raw material, a molybdenum raw material, and a tungsten raw material with a solvent to prepare a solution or slurry (liquid A) having a pH of 0.1 to 4; (ii) drying liquid A to obtain a dried product; and (iii) calcining the dried product to obtain a calcined product. The method for producing a catalyst for methacrylic acid production according to this embodiment may further include a molding step, which will be described later.

[0022] Each step will be described in detail below. <Step (i)> In step (i), a phosphorus source, a molybdenum source, and a tungsten source are mixed with a solvent to prepare a solution or slurry (liquid A) having a pH of 0.1 to 4. Liquid A may contain a source of an element other than phosphorus, molybdenum, and tungsten in formula (I), and it is preferable to contain a source of element G. Liquid A can be prepared by dissolving or suspending raw materials for the catalyst components, including the phosphorus source, the molybdenum source, and the tungsten source, in a solvent.

[0023] (Raw materials for catalyst components) The raw materials for the catalyst components are not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halides, oxoacids, oxoacid salts, etc. of each constituent element of the catalyst can be used alone or in combination of two or more.

[0024] Examples of phosphorus raw materials include phosphoric acid, phosphorus pentoxide, ammonium phosphate, etc. Examples of molybdenum raw materials include molybdenum oxides such as molybdenum trioxide, ammonium molybdates such as ammonium paramolybdate and ammonium dimolybdate, and molybdenum chloride.

[0025] Examples of tungsten raw materials include tungsten oxide, sodium tungstate, phosphotungstic acid, and ammonium metatungstate. Preferably, the tungsten raw material having a solubility of 4.1 g / 100 mL or more in water at 20° C. accounts for 50% by mass or more of the total tungsten raw material. This allows for efficient formation of a heteropolyacid in which the polyatom is tungsten, making it easy to obtain a catalyst in which C / (A+B+C) is within the specified range. Examples of tungsten raw materials having a solubility of 4.1 g / 100 mL or more in water at 20° C. include phosphotungstic acid and ammonium metatungstate. More preferably, the tungsten raw material having a solubility of 4.1 g / 100 mL or more in water at 20° C. accounts for 70% by mass or more, and even more preferably 90% by mass or more.

[0026] When a catalyst containing vanadium and copper is produced, examples of the vanadium raw material include ammonium metavanadate, vanadium pentoxide, vanadium chloride, vanadyl oxalate, etc. Examples of the copper raw material include copper sulfate, copper nitrate, copper oxide, copper carbonate, copper acetate, copper chloride, etc.

[0027] The concentration of the raw materials of the catalyst components in Solution A is not particularly limited, but is preferably in the range of 5 to 90 mass %.

[0028] (Solvent) Examples of the solvent include water, ethyl alcohol, and acetone. These may be used alone or in combination of two or more. Among these, water is preferably used from an industrial viewpoint.

[0029] (Preparation of Solution A) Solution A is preferably prepared by adding raw materials for the catalyst components to a solvent in a preparation vessel and stirring the mixture while heating, thereby producing a sufficient amount of heteropolyacid suitable for the production of methacrylic acid.

[0030] The heating temperature can usually be in the range of 30 to 150°C, but is preferably in the range of 60 to 150°C. By setting the heating temperature to 60°C or higher, the rate of production of the heteropolyacid can be sufficiently increased, and by setting the heating temperature to 150°C or lower, evaporation of the solvent can be suppressed. The lower limit of the heating temperature is more preferably 80°C or higher, and even more preferably 90°C or higher. The upper limit of the heating temperature is more preferably 130°C or lower, and even more preferably 110°C or lower. Depending on the vapor pressure of the solvent used, the heating may involve concentration or reflux, or the heating may be carried out under pressurized conditions by operating in a sealed container.

[0031] The temperature rise rate is not particularly limited, but is preferably 0.8 to 15°C / min. When the temperature rise rate is 0.8°C / min or more, the time required for step (i) can be shortened. Furthermore, when the temperature rise rate is 15°C / min or less, the temperature can be raised using ordinary heating equipment.

[0032] The stirring power was 0.01 kW / m 3 It is preferable to operate at a power of 0.05 kW / m or more. 3 It is more preferable to carry out the stirring at a power of 0.01 kW / m or more. 3 By setting the temperature and components of Solution A at or above 3.5 kW / m, local variations in temperature are reduced, and a structure suitable for use as a catalyst for producing α,β-unsaturated carboxylic acid is stably formed. 3 It is preferable to do the following:

[0033] (Physical Properties of Solution A) The pH of Solution A is 0.1 to 4, with a lower limit of 0.5 or more and an upper limit of 3 or less. This stabilizes the reaction for producing a heteropolyacid suitable for producing an α,β-unsaturated carboxylic acid. Examples of methods for adjusting the pH of Solution A to 0.1 to 4 include using molybdenum trioxide as a molybdenum raw material, or appropriately selecting a raw material compound and adjusting the content of nitrate ions and oxalate ions.

[0034] <Step (ii)> In step (ii), the solution A obtained in step (i) is spray-dried to obtain a dried product. Examples of drying methods include known methods such as drum drying, flash drying, evaporation to dryness, and spray drying. Among these, spray drying is preferred because it can obtain a particulate dried product and the dried product has a regular spherical shape.

[0035] The drying temperature varies depending on the drying method, but can usually be 100 to 500°C, with the lower limit preferably being 140°C or higher and the upper limit preferably being 400°C or lower. Drying is preferably carried out so that the moisture content of the resulting dried product is 4.5% by mass or less, more preferably 0.1 to 4.5% by mass. These conditions are not particularly limited and can be selected appropriately depending on the desired shape and size of the dried product. The dried product obtained in step (ii) may be shaped as described below, if necessary.

[0036] <Shaping Step> In the shaping step, the dried product obtained in the step (ii) is shaped as needed. Note that shaping may be performed after the step (iii) described below.

[0037] The molding method is not particularly limited, and known dry and wet molding methods can be applied, such as tablet molding, press molding, extrusion molding, and granulation molding. The shape of the molded product is not particularly limited, and examples include cylindrical, ring-shaped, spherical, and other shapes. Furthermore, during molding, it is preferable to mold only the dried product without adding a carrier or the like to the dried product, but known additives such as graphite and talc may be added as necessary. When a carrier is used, the carrier is not particularly limited, but silica is preferred.

[0038] <Step (iii)> In the firing step, the dried product obtained in the step (iii) and the shaped dried product obtained in the shaping step are fired to obtain a fired product.

[0039] The calcination can be carried out under a flow of at least one of an oxygen-containing gas such as air and an inert gas, and is preferably carried out under a flow of an oxygen-containing gas such as air. Here, the inert gas refers to a gas that does not reduce the catalytic activity, and examples thereof include nitrogen, carbon dioxide, helium, and argon. These gases may be used alone or in combination of two or more.

[0040] The shape of the firing vessel is not particularly limited, but a box-shaped, tubular, or other vessel can be used. Furthermore, the material can be divided and filled into multiple vessels for firing. Among these, a vessel with a cross-sectional area of ​​1 to 100 cm is particularly suitable. ２ It is preferable to use a tubular container in which

[0041] The firing temperature (maximum temperature during firing) is preferably 200 to 700°C, with the lower limit being more preferably 320°C or higher and the upper limit being more preferably 450°C or lower.

[0042] The calcined product obtained as described above can be used as a catalyst for producing methacrylic acid. The calcined product may also be molded as described in the molding step. In this embodiment, the calcined product and the calcined product after molding are collectively referred to as catalysts.

[0043] [Method for producing methacrylic acid] In the method for producing methacrylic acid according to this embodiment, methacrolein is oxidized using the catalyst for producing methacrylic acid according to this embodiment. Furthermore, in the method for producing methacrylic acid according to this embodiment, methacrolein is oxidized using the catalyst for producing methacrylic acid produced by the production method according to this embodiment. According to these methods, methacrylic acid can be produced with a high yield.

[0044] The method for producing methacrylic acid according to this embodiment can be carried out by contacting the catalyst for producing methacrylic acid according to this embodiment with a raw material gas containing methacrolein. A fixed-bed reactor can be used for this reaction. The reaction can be carried out by filling the reactor with the catalyst and supplying the raw material gas to the reactor. The catalyst layer may be a single layer, or multiple catalysts with different activities may be packed in multiple layers. In addition, the catalyst may be diluted with an inert carrier and packed to control the activity.

[0045] The methacrolein concentration in the raw material gas is preferably 1 to 20% by volume, more preferably 3% by volume or more and 10% by volume or less. The raw material methacrolein may contain small amounts of impurities such as lower saturated aldehydes that do not substantially affect the reaction.

[0046] The oxygen source for the raw material gas is not particularly limited, but it is industrially advantageous to use air. Furthermore, if necessary, a gas obtained by mixing pure oxygen with air or the like can also be used. The ratio of oxygen in the raw material gas is not particularly limited, but is preferably 0.4 to 4 moles per mole of methacrolein, with the lower limit being more preferably 0.5 moles or more and the upper limit being 3 moles or less.

[0047] From an economical viewpoint, the raw material gas may be diluted with an inert gas such as nitrogen or carbon dioxide. Furthermore, water vapor may be added to the raw material gas. By carrying out the reaction in the presence of water vapor, methacrylic acid can be obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably 0.1 to 50% by volume, with the lower limit being 1% by volume or more and the upper limit being more preferably 40% by volume.

[0048] The contact time between the raw material gas and the catalyst for producing methacrylic acid is preferably 1.5 to 15 seconds, more preferably 2 seconds or more at the lower limit and 10 seconds or less at the upper limit. The reaction pressure is preferably 0.1 to 1 MPa (G), where (G) means gauge pressure. The reaction temperature is preferably 200 to 450°C, more preferably 250°C or more at the lower limit and 400°C or less at the upper limit.

[0049] In the production of methacrylic acid, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and a commonly used form can be applied.

[0050] [Method for producing methacrylic acid ester] In the method for producing a methacrylic acid ester according to the present embodiment, the methacrylic acid produced by the method for producing the methacrylic acid according to the present embodiment is esterified. That is, the method for producing a methacrylic acid ester according to the present embodiment includes a step of producing methacrylic acid by the method for producing the methacrylic acid according to the present embodiment and a step of esterifying the methacrylic acid.

[0051] The alcohol to be reacted with methacrylic acid is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Examples of the methacrylic acid ester obtained include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acidic catalyst such as a sulfonic acid-type cation exchange resin. The temperature during the esterification reaction is preferably 50 to 200°C.

[0052] The pressure during the esterification reaction, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and any commonly used form can be applied.

[0053] Hereinafter, examples of producing the catalyst according to this embodiment and examples of reactions using the catalyst will be described together with comparative examples. In the following examples and comparative examples, "parts" means parts by mass.

[0054] (Composition Ratio of Catalyst) The molar ratio of each component was determined by dissolving the catalyst in aqueous ammonia and analyzing the components by ICP emission spectrometry.

[0055] ( ３１ P-NMR measurement) ３１ P-NMR spectra were measured at room temperature using an AVANCE 300 (manufactured by Bruker) with 300 mg of powdered catalyst packed into a sample tube. A 7 mm MAS probe was used for the measurements, and the measurement conditions were a resonance frequency of 121.4 MHz, a pulse width of 5.5 μs, a signal acquisition time of 0.066 s, an accumulation count of 64, a repeat waiting time of 150 s, and an MAS rotation speed of 5000 Hz. The horizontal axis represents the chemical shift (ppm), and the vertical axis represents the detection signal. ３１ In the P-NMR spectrum, the absolute values ​​of the areas calculated by division quadrature for signals observed in the ranges of -5.2 ppm or more and less than 0 ppm, -10 ppm or more and less than -5.2 ppm, and -20 ppm or more and less than -10 ppm were designated A, B, and C, respectively. The horizontal axis was set to the chemical shift of an 85% aqueous phosphoric acid solution, with 0 ppm being the chemical shift.

[0056] (Thermal decomposition temperature of catalyst) The thermal decomposition temperature, which is an index of the heat resistance of the catalyst, was measured using a TG / DTA measurement device as follows. Using 50 mg of alumina as a reference, 50 mg of powdered catalyst was heated from room temperature to 550°C at a rate of 10°C / min in an air atmosphere. In the temperature range of 380°C or higher on the obtained DTA curve, the exothermic onset temperature at which heat of 1.8 μV or more was observed with a temperature rise of 15°C was defined as the thermal decomposition temperature. A higher thermal decomposition temperature of the catalyst means higher heat resistance.

[0057] (Analysis of Raw Material Gas and Product) The raw material gas and product were analyzed using the following gas chromatography: GC-2014 manufactured by Shimadzu Corporation (column: DB-FFAP manufactured by J&W, 30 m×0.32 mm, film thickness 1.0 μm) GC-8A manufactured by Shimadzu Corporation (column: molecular sieve, 2.0 M×3.0 mm ID) GC-8A manufactured by Shimadzu Corporation (column: Porapak Q, 2.0 M×3.0 mm ID) The yield of methacrolein was calculated using the following formula: Yield of methacrylic acid (%)=(N2 / N1)×100 Here, N1 is the number of moles of methacrolein supplied, and N2 is the number of moles of methacrylic acid produced.

[0058] (Tungsten Raw Materials) The tungsten raw materials used in the Examples and Comparative Examples are as follows: Ammonium metatungstate (manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) Solubility in water at 20°C: 10 g / 100 mL Phosphotungstic acid (manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) Solubility in water at 20°C: 40 g / 100 mL or more

[0059] Example 1: 294.0 parts of molybdenum trioxide, 10.2 parts of ammonium metavanadate, 10.6 parts of ammonium metatungstate, a dilution of 30.0 parts of an 85% by weight aqueous phosphoric acid solution with 36 parts of pure water, and a solution of 6.3 parts of copper (II) nitrate trihydrate in 9.0 parts of pure water were mixed into 1200 parts of room temperature pure water. The resulting slurry was heated to 95°C at a rate of 2°C / min and stirred for 2 hours. Next, a solution of 40.4 parts of cesium bicarbonate in 60 parts of room temperature pure water was mixed with the mixture and stirred at 95°C for 15 minutes. Next, a solution of 27.5 parts of ammonium carbonate in 78 parts of pure water was mixed with the mixture and stirred at 95°C for 15 minutes to obtain Solution A. The pH of Solution A is shown in Table 1. The resulting Solution A was heated and evaporated to dryness to obtain a dried product. The dried product was press-molded, crushed, and classified using a sieve to have a particle size ranging from 710 μm to 2.36 mm. The resulting granulated product was calcined at 380° C. for 5 hours in an air stream, and the calcined product was used as a catalyst. The composition of the catalyst, excluding oxygen, was: １．５ Mo １１．８ W ０．２ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１ P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. 8 g of the obtained catalyst was diluted with 10 g of silicon carbide and packed into a fixed-bed flow reactor. Next, a feed gas consisting of 5 vol % methacrolein, 10 vol % oxygen, 30 vol % steam, and 55 vol % nitrogen was passed through the reactor for a contact time of 178 hr·g / mol, and an oxidation reaction of methacrolein was carried out at a reaction temperature of 300°C. The reaction results are shown in Table 1. Example 2 Solution A was obtained in the same manner as in Example 1, except that the amount of molybdenum trioxide was 292.1 parts and the amount of ammonium metatungstate was 13.6 parts. The pH of Solution A is shown in Table 1. The obtained Solution A was heated, evaporated, dried, and solidified to obtain a dried product. A catalyst was obtained using the obtained dried product in the same manner as in Example 1. The composition of the catalyst excluding oxygen was P １．５ Mo １１．７ W ０．３ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1. Example 3 Solution A was obtained in the same manner as in Example 1, except that 287.1 parts of molybdenum trioxide and 22.6 parts of ammonium metatungstate were used. The pH of Solution A is shown in Table 1. The obtained Solution A was heated and evaporated to dryness to obtain a dried product. A catalyst was obtained in the same manner as in Example 1 using the obtained dried product. The composition of the catalyst excluding oxygen was P １．５ Mo １１．５ W ０．５ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１ P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1.

[0060] Example 4 Solution A was obtained in the same manner as in Example 1, except that 285.0 parts of molybdenum trioxide, 29.0 parts of an 85 mass% aqueous phosphoric acid solution, and 29.7 parts of phosphotungstic acid were used instead of 10.6 parts of ammonium metatungstate. The pH of Solution A is shown in Table 1. The obtained Solution A was heated and evaporated to dryness to obtain a dried product. A catalyst was obtained in the same manner as in Example 1 using the obtained dried product. The composition of the catalyst excluding oxygen was P １．５ Mo １１．４ W ０．６ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1. Example 5 Solution A was obtained in the same manner as in Example 1, except that 277.2 parts of molybdenum trioxide and 40.8 parts of ammonium metatungstate were used. The pH of Solution A is shown in Table 1. The obtained Solution A was heated and evaporated to dryness to obtain a dried product. A catalyst was obtained in the same manner as in Example 1 using the obtained dried product. The composition of the catalyst excluding oxygen was P １．５ Mo １１．１ W ０．９ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１ P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1.

[0061] Comparative Example 1 Solution A was obtained in the same manner as in Example 1, except that 270.0 parts of molybdenum trioxide and 53.2 parts of ammonium metatungstate were used. The pH of Solution A is shown in Table 1. The obtained Solution A was heated, evaporated, dried, and solidified to obtain a dried product. Using the obtained dried product, a catalyst was produced in the same manner as in Example 1. The composition of the catalyst, excluding oxygen, was as follows: P １．５ Mo １０．８ W １．２ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１ P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1.

[0062] Comparative Example 2 Solution A was obtained in the same manner as in Example 1, except that 255.0 parts of molybdenum trioxide and 79.8 parts of ammonium metatungstate were used. The pH of Solution A is shown in Table 1. The obtained Solution A was heated, evaporated, dried, and solidified to obtain a dried product. Using the obtained dried product, a catalyst was produced in the same manner as in Example 1. The composition of the catalyst excluding oxygen was: P １．５ Mo １０．２ W １．８ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１ P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1.

[0063] Comparative Example 3 Solution A was obtained in the same manner as in Example 1, except that 270.0 parts of molybdenum trioxide, 27.4 parts of an 85 mass % aqueous phosphoric acid solution, and 59.4 parts of phosphotungstic acid were used instead of 10.6 parts of ammonium metatungstate. The pH of Solution A is shown in Table 1. The obtained Solution A was heated, evaporated, dried, and solidified to obtain a dried product. A catalyst was produced in the same manner as in Example 1 using the obtained dried product. The composition of the catalyst, excluding oxygen, was as follows: P １．４７ Mo １０．８ W １．２ V ０．５ Cu ０．１５ Cs １．２ In addition, the catalyst ３１ P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1.

[0064] Comparative Example 4 300.0 parts of phosphotungstic acid was pressure-molded, crushed, and classified using a sieve so that the particle size was within the range of 710 μm to 2.36 mm. The resulting granulated product was calcined at 380° C. for 5 hours in an air stream, and the calcined product was used as a catalyst. The composition of the catalyst excluding oxygen was: P １ W １２ In addition, the catalyst ３１P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1.

[0065] Comparative Example 5 300.0 parts of phosphomolybdic acid (manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) was calcined at 380°C for 5 hours, and the resulting powder was crushed and classified using a sieve so that the particle size was in the range of 710 μm to 2.36 mm. The resulting granulated product was calcined at 380°C for 5 hours in an air stream to produce a catalyst. The composition of the catalyst excluding oxygen was: P １ Mo １２ In addition, the catalyst ３１ P-NMR measurement and measurement of thermal decomposition temperature were carried out. The results are shown in Table 1. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1. The reaction results are shown in Table 1.

[0066]

[0067] As shown in Table 1, ３１ In Examples 1 to 5, which used catalysts having a C / (A+B+C) within the specified range in the P-NMR spectrum, the thermal decomposition temperature of the catalyst was high and methacrylic acid could be obtained in high yield. Note that methacrylic acid esters can be obtained by esterifying the methacrylic acid obtained in this example.

[0068] According to the present invention, it is possible to provide a catalyst which has high heat resistance and is capable of producing methacrylic acid in a high yield.

Claims

1. A catalyst used in producing methacrylic acid by oxidation of methacrolein, The catalyst contains a heteropolyacid containing phosphorus, molybdenum, and tungsten; The catalyst ３１ In the P-NMR spectrum, when the area of ​​the signal observed in the range of -5.2 ppm or more and less than 0 ppm is A, the area of ​​the signal observed in the range of -10 ppm or more and less than -5.2 ppm is B, and the area of ​​the signal observed in the range of -20 ppm or more and less than -10 ppm is C, C / (A+B+C) is 0.015 to 0.

085. A catalyst for producing methacrylic acid.

2. The aforementioned ３１ The catalyst for producing methacrylic acid according to claim 1, wherein in the P-NMR spectrum, B / (A + B + C) is 0.1 to 0.

485.

3. The aforementioned ３１ The catalyst for producing methacrylic acid according to claim 1 or 2, wherein in the P-NMR spectrum, A / (A + B + C) is 0.5 to 0.

885.

4. The aforementioned ３１ The catalyst for producing methacrylic acid according to claim 1, wherein in the P-NMR spectrum, C / (A + B + C) is 0.02 to 0.

08.

5. The aforementioned ３１ The catalyst for producing methacrylic acid according to claim 4, wherein B / (A + B + C) is 0.2 to 0.45 in the P-NMR spectrum.

6. The aforementioned ３１ The catalyst for producing methacrylic acid according to claim 4 or 5, wherein A / (A + B + C) is 0.53 to 0.75 in the P-NMR spectrum.

7. The catalyst for producing methacrylic acid according to claim 1, having a composition represented by the following formula (I): P ａ Mo ｂ W ｃ V ｄ Cu ｅ A ｆ E ｇ G ｈ O ｉ (I) In formula (I), P, Mo, W, V, Cu, and O represent phosphorus, molybdenum, tungsten, vanadium, copper, and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, tellurium, selenium, and silicon. E represents at least one element selected from the group consisting of iron, zinc, chromium, tantalum, cobalt, nickel, manganese, titanium, and niobium. G represents potassium, rubidium, and niobium. represents at least one element selected from the group consisting of cesium and cesium, a to i represent the molar ratio of each component, where b+c=12, a=0.5 to 3, c=0.22 to 5, d=0.01 to 3, e=0.01 to 2, f=0 to 3, g=0 to 3, h=0.01 to 3, and i is the molar ratio of oxygen required to satisfy the valence of each component.

8. The catalyst for producing methacrylic acid according to claim 7, wherein, in the formula (I), c = 0.22 to 3.

9. A method for producing the catalyst for producing methacrylic acid according to claim 1, (i) mixing a phosphorus source, a molybdenum source, and a tungsten source with a solvent to prepare a solution or slurry (liquid A) having a pH of 0.1 to 4; (ii) drying the solution A to obtain a dried product; (iii) calcining the dried product to obtain a calcined product; A method for producing a catalyst for producing methacrylic acid, comprising:

10. 10. The method for producing a catalyst for methacrylic acid production according to claim 9, wherein in the step (i), the tungsten raw material having a solubility in water at 20 ° C. of 4.1 g / 100 mL or more accounts for 50 mass% or more of the total tungsten raw material.

11. The method for producing a catalyst for methacrylic acid production according to claim 9 or 10, wherein in the step (i), the pH of the A solution is 0.1 to 3.

12. A method for producing methacrylic acid, comprising a step of oxidizing methacrolein using the catalyst for producing methacrylic acid according to claim 1 to produce methacrylic acid.

13. A method for producing methacrylic acid, comprising a step of oxidizing methacrolein using the catalyst for producing methacrylic acid produced by the method according to claim 9 to produce methacrylic acid.

14. A method for producing a methacrylic acid ester, comprising a step of esterifying methacrylic acid produced by the method according to claim 12 or 13.