Catalyst for the production of methacrolein, method for producing the same, and method for producing methacrolein

Abstract

To provide a methacrolein production catalyst enabling methacrolein to be produced in good yield.SOLUTION: A methacrolein production catalyst is provided which includes a heteropolyacid having a composition represented by the following formula (I), and is for use in production of methacrolein by an oxidative dehydrogenation reaction of isobutyraldehyde. PaMobXcYdOe (I). (In formula (I), each of P, Mo and O represents phosphorus, molybdenum and oxygen. X represents at least one selected from transition metal elements. Y represents at least one selected from alkali metal elements and ammonium cations. a to e represent the molar ratio of respective component, and when b=12, 1<a≤2, 0<c≤12, 9≤b / a+c≤15, 0≤d≤18, e is the molar ratio of oxygen required to satisfy the valence of the respective component.).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a catalyst for the production of methacrolein, a method for producing the same, and a method for producing methacrolein. [Background technology]

[0002] Methacrolein is an industrially important compound as a synthetic intermediate for methacrylic acid and methyl methacrylate. A known method for producing methacrolein involves the oxidative dehydrogenation of isobutyraldehyde in the presence of a catalyst, and various catalysts have been proposed.

[0003] For example, Patent Document 1 proposes a compound or mixture consisting of an oxide containing one or more of zinc, copper, and silver, a molybdenum oxide, and a phosphorus compound as a catalyst for producing methacrolein and methacrylic acid from isobutyraldehyde.

[0004] Furthermore, Patent Document 2 describes a catalyst for producing methacrolein from isobutyraldehyde, with the general formula Fe a P b Pb c O d A composition represented by the formula has been proposed (wherein Fe is iron, P is phosphorus, Pb is lead, and O is oxygen, and the subscripts a, b, c, and d indicate the number of atoms, with a being 1, b taking values ​​from 0.7 to 3, and c taking values ​​from 0.01 to 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 54-046705 [Patent Document 2] Japanese Patent Application Publication No. 7-53435 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the production of methacrolein using the aforementioned catalyst was still insufficient from the viewpoint of methacrolein yield. Therefore, further improvement is desired from an industrial standpoint. Specifically, an object of the present invention is to provide a catalyst for producing methacrolein (hereinafter also simply referred to as "the catalyst") that is capable of producing methacrolein in a high yield. Means for Solving the Problems

[0007] The present invention has been made in view of the aforementioned circumstances, and the present inventors have found that the aforementioned problems can be solved by using a catalyst for producing methacrolein having a specific composition ratio, and have thereby completed the present invention.

[0008] The gist of the present invention is as follows. [1]: A catalyst for producing methacrolein, which is used when producing methacrolein by oxidative dehydrogenation reaction of isobutyraldehyde, the catalyst comprising a heteropolyacid having a composition represented by the following formula (I). P a Mo b X c Y d O e (I) (In formula (I), P, Mo and O represent phosphorus, molybdenum and oxygen, respectively. X represents at least one element selected from transition metal elements. Y represents at least one selected from alkali metal elements and ammonium cations. a to e represent the molar ratio of each component, and when b=12, 1<a≦2, 0<c≦12, 9≦b / a+c≦15, 0≦d≦18, and e is the molar ratio of oxygen required to satisfy the valences of the aforementioned respective components.) [2]: The catalyst for producing methacrolein according to [1], wherein in the aforementioned formula (I), X comprises at least one element selected from Group 5 transition metal elements of the periodic table. [3]: The catalyst for producing methacrolein according to [1] or [2], wherein in the aforementioned formula (I), X comprises niobium. [4]: The catalyst for producing methacrolein according to any one of [1] to [3], wherein in the aforementioned formula (I), Y comprises at least one selected from potassium, cesium and ammonium cations. [5]: The catalyst for producing methacrolein according to any one of [1] to [4], wherein in the aforementioned formula (I), 1<a≦1.4 and 0<c≦4.0. [6]: In the infrared absorption spectrum obtained by FT-IR measurement, 870cm -1 ±10cm -1 where the absorbance of the maximum peak within the range is defined as A1, and the absorbance of the maximum peak within the range of 1065±10cm -1 is defined as A2, A1 / A2 is 1 or more, the catalyst for producing methacrolein according to any one of [1] to [5]. [7]: The catalyst for producing methacrolein according to [6], wherein in the infrared absorption spectrum obtained by FT-IR measurement, the aforementioned A1 / A2 is 1.05 or more. [8]: A method for producing the catalyst for producing methacrolein according to any one of [1] to [7], comprising the following steps (i) to (iii). (i) A step of preparing a solution or slurry (S1) containing a heteropolyacid containing at least phosphorus and molybdenum. (ii) A step of adding a raw material compound of element X to the aforementioned solution or slurry (S1) to prepare a solution or slurry (S2). (iii) A step of drying the aforementioned solution or slurry (S2) to obtain a solid matter. [9]: The method for producing a catalyst for producing methacrolein according to [8], wherein in the aforementioned step (ii), after adding the raw material compound of element X to the aforementioned slurry (S1), centrifugation is performed to obtain a supernatant liquid, thereby preparing the aforementioned solution or slurry (S2).

[10] : The method for producing a catalyst for producing methacrolein according to [9], wherein in the aforementioned step (ii), the aforementioned supernatant liquid is subjected to ion exchange using a strongly acidic cation exchange resin, thereby preparing the aforementioned solution or slurry (S2).

[11] : A method for producing a catalyst for the production of methacrolein according to any one of [8] to

[10] , wherein the drying in step (iii) is freeze-drying.

[12] : A method for producing methacrolein, comprising producing methacrolein from isobutyraldehyde using a methacrolein production catalyst described in any of [1] to [7].

[13] : A method for producing methacrolein, comprising producing methacrolein by an oxidative dehydrogenation reaction of isobutyraldehyde using a catalyst for producing methacrolein produced by the methods described in [8] to

[11] . [Effects of the Invention]

[0009] According to the present invention, a catalyst for producing methacrolein that can produce methacrolein in high yield by the oxidative dehydrogenation reaction of isobutyraldehyde, a method for producing the same, and a method for producing methacrolein can be provided. [Modes for carrying out the invention]

[0010] The following describes embodiments of the present invention, but the present invention is not limited to the following. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, and "A~B" means that it is greater than or equal to A and less than or equal to B.

[0011] [Catalyst for Metacrolein Production] (Composition of the catalyst) A catalyst for the production of methacrolein according to one embodiment of the present invention is used in the production of methacrolein by the oxidative dehydrogenation reaction of isobutyraldehyde and contains a heteropoly acid having a composition represented by the following formula (I). In this specification, the molar ratios of each element are determined by analyzing the components obtained by dissolving the catalyst in ammonia water using ICP emission spectrometry. The molar ratio of ammonium cations is determined by analyzing the catalyst using the Kjeldahl method. P a Mo b X c Y dO e (I) (In formula (I), P, Mo and O represent phosphorus, molybdenum and oxygen respectively. X represents at least one element selected from transition metal elements. Y represents at least one species selected from alkali metal elements and ammonium cations. a to e represent the molar ratio of each component, and when b=12, 1<a≦2, 0<c≦12, 9≦b / a+c≦15, 0≦d≦18, and e is the molar ratio of oxygen required to satisfy the valence of each of the aforementioned components.) By using such a catalyst, methacrolein can be produced at a high yield in the oxidative dehydrogenation reaction of isobutyraldehyde.

[0012] Since the catalyst for methacrolein production contains the heteropolyacid having the composition represented by the aforementioned formula (I), the conversion rate of isobutyraldehyde is improved, and methacrolein can be obtained at a high yield. Regarding this mechanism, it is considered that, as shown in the aforementioned formula (I), the heteropolyacid contains a transition metal, so that a catalyst for methacrolein production having favorable oxidation properties in the oxidative dehydrogenation reaction of isobutyraldehyde can be obtained.

[0013] In the aforementioned formula (I), X represents at least one element selected from transition metal elements. From the viewpoint of methacrolein yield, X preferably contains at least one element selected from Group 5 transition metal elements of the periodic table, more preferably contains at least one selected from vanadium and niobium, and further preferably contains niobium.

[0014] In the aforementioned formula (I), Y represents at least one species selected from alkali metal elements and ammonium cations. From the viewpoint of methacrolein yield, Y preferably contains at least one species selected from lithium, sodium, potassium, cesium, rubidium and ammonium cations, and more preferably contains at least one species selected from potassium, cesium and ammonium cations. The alkali metal elements may be used alone or in combination of two or more.

[0015] In the aforementioned formula (I), from the viewpoint of being able to produce methacrolein at a high yield, when b=12, the following conditions can be applied to a, c, and d: 1<a≦2, preferably 1<a≦1.4, more preferably 1<a≦1.2; 0<c≦12, preferably 0<c≦4.0, more preferably 0<c≦2.5; 9≦b / a+c≦15, preferably 10≦b / a+c≦14, more preferably 11≦b / a+c≦13; and 0≦d≦18, preferably 0≦d≦12, more preferably 0≦d≦10.

[0016] (Infrared absorption spectrum of catalyst) The catalyst for producing methacrolein according to the present embodiment preferably contains a Keggin-type heteropolyacid from the viewpoint of methacrolein yield. The structure of the heteropolyacid can be determined by FT-IR measurement. When the catalyst contains a Keggin-type heteropolyacid, the obtained infrared absorption spectrum shows 1065cm -1 ±10cm -1 , 960cm -1 ±10cm -1 , 870cm -1 ±10cm -1 , 780cm -1 ±10cm -1 has characteristic peaks. Examples of the method for obtaining the catalyst for producing methacrolein containing a Keggin-type heteropolyacid include a method of adjusting the pH of the resulting solution or slurry (S2) to 4 or lower in step (ii) described later, or a production method including a calcination step. Moreover, regarding the catalyst for producing methacrolein according to the present embodiment, in the infrared absorption spectrum, the absorbance of the maximum peak within the range of 870cm -1 ±10cm -1 is defined as A1, and the absorbance at 1065cm -1 ±10cm -1When the absorbance of the maximum peak within the specified range is denoted as A2, it is preferable that A1 / A2 be 1 or greater, and more preferably 1.05 or greater. Furthermore, there is no particular upper limit to A1 / A2, but it is usually 2 or less, and may also be 1.5 or less, or 1.35 or less. By using a catalyst having the above-mentioned A1 / A2 values, methacrolein can be produced in high yield. The reasons for this are thought to be as follows. In the infrared absorption spectrum of a catalyst for the production of methacrolein, an A1 / A2 ratio of 1 or greater indicates that many heteropoly acids contain element X in formula (I) as polyatoms. It is believed that using a catalyst containing such heteropoly acids will further improve the yield of methacrylic acid. A method for obtaining a methacrolein production catalyst having the above infrared absorption spectrum can be, for example, a method for producing the catalyst that includes steps (i) to (iii) described later. The equipment used for FT-IR measurements includes the NICOLET6700FT-IR (product name, manufactured by Thermo Electron), etc., with a range of 1200-2000 cm². -1 An apparatus capable of measuring within this range can be used. The measurement method shall be the transmission method, and shall be performed as follows: KBr shall be used as a diluent, and the mixture shall be formed into pellets using a tablet molding machine. Next, the catalyst shall be diluted and mixed with KBr so that the concentration is 0.5 to 1 mass%, and similarly formed into pellets for measurement. For the obtained infrared absorption spectrum, the vertical axis shall be absorbance and the horizontal axis shall be wavenumber, and the measurement shall be performed at 1200 cm⁻¹. -1 A horizontal baseline correction was performed so that the absorbance at that point was 0. From the corrected infrared absorption spectrum obtained, A1 / A2 was calculated.

[0017] [Methacrolein production method for catalyst] The method for producing the methacrolein catalyst according to the above embodiment is not particularly limited, but it is preferable that it be produced by a method comprising the following steps (i) to (iii), which is a method for producing the methacrolein catalyst according to another embodiment of the present invention. (i) A step of preparing a solution or slurry (S1) containing a heteropoly acid that contains at least phosphorus and molybdenum. (ii) A step of preparing a solution or slurry (S2) by adding a raw material compound of element X to the solution or slurry (S1). (iii) A step of drying the solution or slurry (S2) to obtain a solid. Furthermore, the method for producing a catalyst for methacrolein according to this embodiment may further include a molding step and a calcination step, which will be described later. The following provides a detailed explanation of each step.

[0018] (Step (i)) In step (i), a solution or slurry (S1) containing a heteropoly acid containing at least phosphorus and molybdenum is prepared. The solution or slurry (S1) is preferably prepared by mixing the raw material compounds of the components included in the composition represented by formula (I) with a solvent. There are no particular restrictions on the raw material compounds used, and examples include nitrates, carbonates, acetates, ammonium salts, potassium salts, oxides, halides, oxoacids, or oxoate salts of each element, and these can also be used in combination. Examples of phosphorus raw materials include orthophosphoric acid, phosphorus pentoxide, or phosphates such as ammonium phosphate. Examples of molybdenum raw materials include ammonium paramolybdate, molybdenum trioxide, molybdic acid, and molybdenum chloride. In addition, phosphomolybdenum heteropoly acids such as phosphomolybdic acid may be used as phosphorus and molybdenum raw materials. The raw material compounds may be used individually or in combination of two or more for each element constituting the catalyst component. There are no particular restrictions on the solvent; water or an organic solvent can be used, but from an industrial standpoint, water is preferred. Use of raw materials other than phosphomolybdenum heteropoly acids as phosphorus and molybdenum raw materials. In this case, it is preferable to mix the raw material compound with the solvent and stir it at a temperature of 60 to 150°C for 0.5 to 24 hours. This preferably produces a heteropoly acid containing phosphorus and molybdenum. The lower limit of the stirring temperature is more preferably 80°C or higher, and even more preferably 90°C or higher. The upper limit of the stirring temperature is more preferably 130°C or lower, and even more preferably 110°C or lower. The lower limit of the stirring time is more preferably 1 hour or more, and the upper limit is more preferably 12 hours or less.

[0019] (Step (ii)) In step (ii), a starting compound of element X is added to the solution or slurry (S1) obtained in step (i) to prepare a solution or slurry (S2). The starting compound of element X is preferably added at a temperature range of 5 to 80°C, with a lower limit of 10°C or higher and a higher limit of 60°C or lower. After adding the starting compound of element X, it is preferable to stir at a temperature of 20 to 120°C for 0.5 to 10 hours. The lower limit of the stirring temperature is preferably 60°C or higher, and the upper limit is more preferably 90°C or lower. The lower limit of the stirring time is preferably 2 hours or higher, and the upper limit is more preferably 5 hours or lower. Furthermore, it is preferable to prepare the solution or slurry (S2) by adding the raw material compound of element X to the solution or slurry (S1), and then centrifuging to obtain the supernatant. This allows for a higher concentration of heteropoly acids containing element X as polyatoms in the catalyst. The centrifugation is preferably performed at a rotational speed of 1,000 to 15,000 rpm, and more preferably at 5,000 to 15,000 rpm. The centrifugation is also preferably performed for 5 to 60 minutes, and more preferably for 10 to 60 minutes. Furthermore, it is preferable to prepare a solution or slurry (S2) by ion exchange of the supernatant obtained by centrifugation using a strongly acidic cation exchange resin. There are no particular restrictions on the method of ion exchange; for example, one method is to pass the solution or slurry (S2) through a container filled with a strongly acidic cation exchange resin. The solution or slurry (S2) may be passed through the same strongly acidic cation exchange resin repeatedly. It is also preferable to use a strongly acidic cation exchange resin in an amount of 0.01 to 100 times the weight of the solution or slurry (S2). The pH of the solution or slurry (S2) is preferably 4 or less, and more preferably 3 or less. Methods for adjusting the pH include appropriately selecting the amount of raw material compound added and adding nitric acid, oxalic acid, etc.

[0020] (Step (iii)) In step (iii), the solution or slurry (S2) obtained in step (ii) is dried to obtain a solid. The drying method and drying temperature are not particularly limited and can be appropriately selected depending on the desired shape and size of the dried product. In the method according to this embodiment, drying can be done by freeze-drying, vacuum drying, drum drying, spray drying, or evaporation to dryness, but freeze-drying, vacuum drying, or spray drying is preferred. This allows the solution or slurry (S2) to be dried at a low temperature, thereby suppressing the decomposition of the heteropoly acid. Among these, freeze-drying is particularly preferred. When freeze-drying is used in step (iii), the conditions are not particularly limited, but typically the solution or slurry (S2) is frozen at a temperature of -200 to 0°C, and then dried in a freeze-dryer at a pressure of 5 to 500 Pa, sublimating the frozen solution or slurry (S2) so that it does not become liquid. The solid obtained in step (iii) exhibits catalytic properties and can be used as a catalyst for the production of methacrolein. However, further molding and calcination, as described later, are preferable as they improve the catalytic performance. In this embodiment, the molded and calcined materials are collectively referred to as catalysts.

[0021] (molding process) In the molding process, the solid obtained in step (iii) is molded as needed to form a molded body. The molding method is not particularly limited, and known dry or wet molding methods can be applied. Examples include tableting, press molding, extrusion molding, or granulation molding. The shape of the molded product is not particularly limited, and examples include cylindrical, ring-shaped, or spherical. Furthermore, it is preferable to mold only the solid material without adding a carrier or binder to the catalyst precursor during molding, but known additives such as graphite or talc, or known binders derived from organic or inorganic materials may be added as needed.

[0022] (Firing process) From the viewpoint of methacrolein yield, it is preferable to calcine the solid obtained in step (iii) or the molded body obtained in the molding step. Calcination can be carried out, for example, under the flow of at least one of an oxygen-containing gas such as air and an inert gas, and is preferably carried out under the flow of an oxygen-containing gas such as air. Here, an inert gas refers to a gas that does not reduce catalytic activity, such as nitrogen, carbon dioxide, helium, or argon. These may be used individually or in mixtures of two or more.

[0023] There are no particular restrictions on the shape of the firing container, but the cross-sectional area should be between 2 and 100 cm². 2 It is preferable to use a tubular heat treatment container. The firing temperature is preferably 300 to 700°C, with a lower limit of 320°C or higher and a higher limit of 450°C or lower.

[0024] [Methacrolein manufacturing method] Another embodiment of the present invention provides a method for producing methacrolene, which includes the step of producing methacrolene by an oxidative dehydrogenation reaction of isobutyraldehyde using the methacrolein production catalyst described above.

[0025] The aforementioned oxidative dehydrogenation method can be carried out by filling a reactor with a catalyst for methacrolein production and supplying a raw material gas containing isobutyraldehyde and oxygen to the reactor. A fixed-bed reactor can be used as the reactor. The catalyst layer may be a single layer, or multiple catalysts with different reactivity may be packed into multiple layers. Furthermore, to control the activity, the catalyst may be diluted with an inert support before packing. The concentration of isobutyraldehyde in the raw material gas is not particularly limited, but is preferably 0.5 to 20% by volume, with a lower limit of 1% or more by volume and a higher limit of 10% or less by volume. Isobutyraldehyde may also contain small amounts of impurities that do not substantially affect this reaction, such as water or lower saturated aldehydes.

[0026] The oxygen concentration in the raw material gas is preferably 1 to 10 moles per mole of isobutyraldehyde. Air is preferred as the oxygen source from an economic standpoint. If necessary, an oxygen-enriched gas may be used by adding pure oxygen to air. The raw material gas may be isobutyraldehyde and oxygen diluted with an inert gas such as nitrogen or carbon dioxide. Furthermore, water vapor may be added to the raw material gas.

[0027] When the raw material gas and the catalyst for methacrolein production are in contact, the W / F ratio expressed by the following formula is 1 to 1000 g·hr / m 3 The following is preferable: W / F = (Mass of methacrolein catalyst packed into the reactor [g]) / (Velocity of raw material gas supplied into the reactor [m]) 3 / hr]) Furthermore, the reaction pressure is preferably 0.1 to 1 MPa (G), where (G) represents gauge pressure. The reaction temperature is preferably 200 to 500°C, with an upper limit of 400°C or less. This is preferable. As a result, the heteropoly acid contained in the catalyst for the production of methacrolein can maintain its structure stably during the reaction. [Examples]

[0028] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Note that "parts" refers to parts by mass. In the following examples, the centrifuge was an AS-ONE AS185, the freeze-drying apparatus was a Tokyo Rikakikai Co., Ltd. FDU-2200, and the ICP measuring apparatus was a PerkinElmer Optima8300.

[0029] (Composition ratio of catalyst for methacrolein production) The molar ratios of each element were determined by analyzing the components of the methacrolein production catalyst dissolved in ammonia water using ICP emission spectrometry. The molar ratio of ammonium cations was determined by analyzing the methacrolein production catalyst using the Kjeldahl method.

[0030] (FT-IR measurement) For FT-IR measurements, a NICOLET6700FT-IR (product name, manufactured by Thermo Electron) was used, and measurements were performed by transmission. First, KBr was formed into pellets using a tablet forming machine, and background measurements were performed. Next, the catalyst was diluted and mixed with KBr to a concentration of 0.5 to 1 mass%, and similarly formed into pellets for measurement. For the obtained infrared absorption spectra, the vertical axis was set to absorbance and the horizontal axis to wavenumber, at 1200 cm⁻¹. -1 A horizontal baseline correction was performed so that the absorbance at that point was 0. From the corrected infrared absorption spectrum obtained, A1 / A2 was calculated.

[0031] (Analysis of source gas and products) The raw material gas and products were analyzed using gas chromatography (instrument: Shimadzu GC-2010, column: J&W DB-FFAP, 30m × 0.32mm, film thickness 1.0μm). From the gas chromatography results, the isobutyraldehyde reaction rate, methacrolein selectivity, and methacrolein yield were determined using the following formulas.

[0032] Isobutyraldehyde reaction rate (%) = Moles of isobutyraldehyde reacted / Moles of isobutyraldehyde supplied × 100

[0033] Metacrolein selectivity (%) = Moles of metacrolein produced / Moles of metacrolein reacted × 100

[0034] Metacrolein yield (%) = Metacrolein reaction rate (%) × Metacrolein selectivity (%) / 100

[0035] [Example 1] Phosphorus-molybdic acid (manufactured by Nippon Inorganic Chemical Industry Co., Ltd., P1Mo 12 3.5 g was mixed with 5 ml of distilled water at room temperature to prepare a solution (S1) containing heteropoly acid. Next, potassium niobate (manufactured by Mitsuwa Chemical Co., Ltd., K8Nb6O 19 A potassium niobate solution was prepared by dissolving 0.37 g of (16.6H2O) in 5 ml of distilled water at room temperature. This potassium niobate solution was added to the solution (S1) obtained above at room temperature and heated at 85°C for 3 hours. Next, the resulting slurry was centrifuged at 11000 rpm for 10 minutes to obtain the supernatant, thereby preparing solution (S2). Next, the obtained solution (S2) was freeze-dried to obtain a solid. The composition of the solid, excluding oxygen, was P 1.1 Mo 12 Nb 1.1 K 1.1 That was the case.

[0036] The obtained solid is packed into the reactor as a catalyst for methacrolein production, and a raw material gas consisting of 1.4% isobutyraldehyde, 10% water vapor, 10% oxygen, and 78.6% nitrogen is introduced at a gas flow rate of 2.3 m³. 3 The catalyst was supplied at a flow rate of / s, and the oxidative dehydrogenation reaction of isobutyraldehyde was carried out at a reaction temperature of 240°C. The weight and W / F of the methacrolein production catalyst packed into the reactor are shown in Table 1. The obtained products were repaired and analyzed using gas chromatography to calculate the reaction rate of isobutyraldehyde, the selectivity of methacrolein, and the yield of methacrolein. The results are shown in Table 1.

[0037] [Example 2] Phosphate vanadomolybdate 1 (manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) was used as a catalyst for the production of methacrolein. The composition of the catalyst excluding oxygen is P 1.1 Mo 12 V 1.1 The oxidative dehydrogenation reaction of isobutyraldehyde was carried out in the same manner as in Example 1, except that the catalyst was used. The weight and W / F of the methacrolein production catalyst packed into the reactor are shown in Table 1. The obtained products were repaired and analyzed using gas chromatography to calculate the reaction rate of isobutyraldehyde, the selectivity of methacrolein, and the yield of methacrolein. The results are shown in Table 1.

[0038] [Example 3] Solution (S1) was prepared in the same manner as in Example 1. Next, the supernatant liquid obtained by centrifugation is subjected to a strongly acidic cation exchange resin H type (Fujifilm Wako Pure Chemical Corporation, Dowex). TM Solution (S2) was prepared in the same manner as in Example 1, except that 5.0 g of (50W50-100) was used for ion exchange. Next, the obtained solution (S2) was freeze-dried to obtain a solid. The composition of the solid, excluding oxygen, was P 1.1 Mo 12 Nb 1.1 That was the case.

[0039] The obtained solid was used as a catalyst for the production of methacrolein, and the oxidative dehydrogenation reaction of isobutyraldehyde was carried out in the same manner as in Example 1. The weight and W / F of the methacrolein production catalyst packed into the reactor are shown in Table 1. The obtained products were repaired and analyzed using gas chromatography to calculate the reaction rate of isobutyraldehyde, the selectivity of methacrolein, and the yield of methacrolein. The results are shown in Table 1.

[0040] [Comparative Example 1] Phosphorus-molybdic acid (manufactured by Nippon Inorganic Chemical Industry Co., Ltd., P1Mo 12 O 40 A phosphomolybdic acid solution was prepared by dissolving 30 g of ) in 100 ml of distilled water. Next, a potassium nitrate solution was prepared by dissolving 1.5 g of potassium nitrate (Fujifilm Wako Pure Chemical Industries, Ltd., KNO3) in 10 ml of distilled water. This potassium nitrate solution was added to the phosphomolybdic acid solution obtained above at room temperature, and the mixture was stirred at room temperature for 1 hour to prepare a slurry (S1) containing heteropoly acid. Next, the obtained slurry (S1) was evaporated to dryness at 90°C to obtain a solid. The oxygen-free composition of the solid was P1Mo 12 It was K1.

[0041] The obtained solid was used as a catalyst for the production of methacrolein, and the oxidative dehydrogenation reaction of isobutyraldehyde was carried out in the same manner as in Example 1. The weight and W / F of the methacrolein production catalyst packed into the reactor are shown in Table 1. The obtained products were repaired and analyzed using gas chromatography to calculate the reaction rate of isobutyraldehyde, the selectivity of methacrolein, and the yield of methacrolein. The results are shown in Table 1.

[0042] [Table 1] As shown in Table 1, Examples 1-3, which used catalysts containing heteropoly acids with specific composition ratios, were able to produce methacrolein in high yield. [Industrial applicability]

[0043] According to the present invention, a catalyst for producing methacrolein can be provided that enables the production of methacrolein in high yield by the oxidative dehydrogenation reaction of isobutyraldehyde.

Claims

1. A catalyst for the production of methacrolein, comprising a heteropoly acid having a composition represented by the following formula (I), used in the production of methacrolein by the oxidative dehydrogenation reaction of isobutyraldehyde. P a Man b X c 6 d 4 ｅ () (In formula (I), P, Mo, and O represent phosphorus, molybdenum, and oxygen, respectively. X contains at least one selected from vanadium and niobium. Y contains at least one selected from potassium, cesium, and ammonium cations. a to e represent the molar ratios of each component, where when b = 12, 1 < a ≤ 2, 0 < c ≤ 12, 9 ≤ b / a + c ≤ 15, 0 ≤ d ≤ 18, and e is the molar ratio of oxygen required to satisfy the valency of each component.)

2. The catalyst for producing methacrolein according to claim 1, wherein in formula (I), X contains niobium.

3. The catalyst for producing methacrolein according to claim 1 or 2, wherein in formula (I), 1 < a ≤ 1.4 and 0 < c ≤ 4.

0.

4. In the infrared absorption spectrum obtained by FT-IR measurement, 870 cm －１ ±10 cm －１ the absorbance of the maximum peak in the range of is defined as A1, and 1065 cm －１ ±10 cm －１ the absorbance of the maximum peak in the range of is defined as A2, A1 / A2 is 1 or more, the catalyst for producing methacrolein according to any one of claims 1 to 3.

5. The catalyst for producing methacrolein according to claim 4, wherein the A1 / A2 ratio in the infrared absorption spectrum obtained by FT-IR measurement is 1.05 or greater.

6. A method for producing a catalyst for the production of methacrolein according to any one of claims 1 to 5, comprising the following steps (i) to (iii). (i) A step of preparing a solution or slurry (S1) containing a heteropoly acid that contains at least phosphorus and molybdenum. (ii) A step of preparing a solution or slurry (S2) by adding a raw material compound of element X to the solution or slurry (S1). (iii) A step of drying the solution or slurry (S2) to obtain a solid.

7. The method for producing a catalyst for producing methacrolein according to claim 6, wherein in step (ii) above, a raw material compound of element X is added to the solution or slurry (S1), and then the solution or slurry (S2) is prepared by centrifugation to obtain the supernatant.

8. The method for producing a catalyst for producing methacrolein according to claim 7, wherein in step (ii), the solution or slurry (S2) is prepared by ion exchange of the supernatant liquid using a strongly acidic cation exchange resin.

9. A method for producing a catalyst for producing methacrolein according to any one of claims 6 to 8, wherein the drying in step (iii) is freeze-drying.

10. A method for producing methacrolein, comprising the step of producing methacrolein from isobutyraldehyde using a methacrolein production catalyst according to any one of claims 1 to 5.

11. A method for producing methacrolein, comprising the step of producing methacrolein by an oxidative dehydrogenation reaction of isobutyraldehyde using a methacrolein production catalyst produced by the manufacturing method described in any one of claims 6 to 9.

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