Method for producing catalyst, method for producing α,β-unsaturated carboxylic acid, and method for producing α,β-unsaturated carboxylic ester

Abstract

To provide a method for producing a catalyst capable of producing an α,β-unsaturated carboxylic acid at a high yield.SOLUTION: A method for producing a catalyst used in the oxidation of α,β-unsaturated aldehydes to produce α,β-unsaturated carboxylic acids, comprising: (i) preparing a slurry (solution A) containing molybdenum, phosphorus, and an ammonium group; (ii-1) mixing the solution A with a raw material compound containing an alkali metal to prepare a slurry (solution B1); (ii-2) mixing the solution B1 with a raw material compound containing an ammonium group to prepare a slurry (solution B2); and (iii) drying the solution B2 to obtain a catalyst, wherein when the number of moles of the ammonium group contained in the solution A is N1 and the number of moles of the ammonium group contained in the solution B2 is N2, N1 / N2 is 0.15 to 0.6.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a catalyst for producing an α,β-unsaturated carboxylic acid, and a method for producing an α,β-unsaturated carboxylic acid and an α,β-unsaturated carboxylic acid ester using the catalyst. [Background technology]

[0002] Heteropolyacid catalysts such as phosphomolybdic acid and phosphomolybdates are known as catalysts for producing α,β-unsaturated carboxylic acids (hereinafter simply referred to as "catalysts") used in the oxidation of α,β-unsaturated aldehydes to produce α,β-unsaturated carboxylic acids. Examples of such 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 also be referred to simply as "heteropolyacids," and proton-type heteropolyacids and / or heteropolyacid salts will also be referred to as "heteropolyacids (salts)"). Known heteropolyacid salts include alkali metal salts in which the cation is an alkali metal ion and ammonium salts in which the cation is an ammonium ion. Many studies have been conducted on methods for producing such catalysts, and most of these involve preparing an aqueous solution or slurry containing the elements that constitute the catalyst, followed by drying and calcining the solution.

[0003] Patent Document 1 discloses a method for producing a precursor of a catalyst for producing an α,β-unsaturated carboxylic acid, in which an ammonium compound containing ammonium carbamate in a specific ratio is used as the ammonium compound in a step of adding an ammonium compound to an aqueous slurry or aqueous solution containing a molybdenum-containing heteropolyacid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 110126 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the catalyst obtained by the method described in Patent Document 1 is used to produce an α,β-unsaturated carboxylic acid, the yield of the α,β-unsaturated carboxylic acid is not necessarily sufficient, and there is a demand for the development of a catalyst that can produce an α,β-unsaturated carboxylic acid in a higher yield.

[0006] An object of the present invention is to provide a method for producing a catalyst capable of producing an α,β-unsaturated carboxylic acid in high yield, and a method for producing an α,β-unsaturated carboxylic acid and an α,β-unsaturated carboxylic acid ester in high yield using the catalyst. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to achieve the above object, and as a result have found that the above problems can be solved by adding a raw material compound containing an ammonium radical in portions at a specific ratio, thereby completing the present invention.

[0008] That is, the present invention includes the following configurations. [1] A method for producing a catalyst used in producing an α,β-unsaturated carboxylic acid by oxidizing an α,β-unsaturated aldehyde, comprising: (i) preparing a slurry (liquid A) containing molybdenum, phosphorus, and ammonium radicals; (ii-1) mixing the solution A with a raw material compound containing an alkali metal to prepare a slurry (solution B1); (ii-2) mixing the B1 solution with a raw material compound containing an ammonium radical to prepare a slurry (B2 solution); (iii) drying the B2 liquid to obtain a catalyst; and A method for producing a catalyst, wherein N1 / N2 is 0.15 to 0.6, where N1 is the number of moles of ammonium radicals contained in the A solution and N2 is the number of moles of ammonium radicals contained in the B2 solution. [2] The method for producing a catalyst according to [1], wherein the N1 / N2 is 0.2 to 0.45. [3] The method for producing a catalyst according to [1] or [2], wherein in step (i), the solution A is prepared by mixing a raw material compound containing molybdenum, a raw material compound containing phosphorus, and a raw material compound containing an ammonium radical with a solvent, and maintaining the mixture under stirring at a temperature of 80°C or higher for one hour or more. [4] A method for producing a catalyst according to any one of [1] to [3], which satisfies at least one of the following formulas (I-1) and (I-2): n1=0.01~4.5 (I-1); m1=6~12 (I-2), In formula (I-1), n1 represents the molar ratio of ammonium radicals contained in the A solution when the molar ratio of molybdenum in the catalyst is 12, and in formula (I-2), m1 represents the molar ratio of molybdenum contained in the B1 solution when the molar ratio of molybdenum in the catalyst is 12. [5] The method for producing the catalyst according to [4], which satisfies both the formula (I-1) and the formula (I-2). [6] The method for producing a catalyst according to any one of [1] to [5], wherein the catalyst has a composition represented by the following formula (II): P a Mo b V c Cu d G e (NH4) f O g (II) In formula (II), P, Mo, V, Cu, NH4, and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively; G represents at least one element selected from the group consisting of alkali metals; a to g represent the molar ratios of each component, where when b=12, a=0.5 to 3, c=0.01 to 3, d=0.01 to 2, e=0.01 to 3, and f=0.01 to 10; and g represents the molar ratio of oxygen necessary to satisfy the valence of each component. [7] The method for producing a catalyst according to any one of [1] to [6], wherein in the step (ii-1), the temperature of the solution A to be mixed with the raw material compound containing an alkali metal is 30°C to 99°C. [8] The method for producing a catalyst according to any one of [1] to [7], wherein in the step (ii-2), the temperature of the liquid B1 mixed with the raw material compound containing the ammonium radical is 30°C to 99°C. [9] A method for producing an α,β-unsaturated carboxylic acid, comprising oxidizing an α,β-unsaturated aldehyde in the presence of a catalyst produced by the method according to any one of [1] to [8].

[10] A method for producing an α,β-unsaturated carboxylic acid ester, which comprises esterifying an α,β-unsaturated carboxylic acid produced by the method described in [9]. [Effects of the Invention]

[0009] According to the present invention, a catalyst capable of producing an α,β-unsaturated carboxylic acid in high yield can be obtained. Furthermore, by using the catalyst, an α,β-unsaturated carboxylic acid and an α,β-unsaturated carboxylic acid ester can be produced in high yield. Furthermore, in a reaction that produces a high yield of an α,β-unsaturated carboxylic acid, the successive oxidation of an α,β-unsaturated aldehyde is suppressed, thereby suppressing the amount of heat generated and enabling stable operation. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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. Furthermore, when a numerical range is written in stages, the upper and lower limits of each numerical range and the numerical values ​​written in the examples can be arbitrarily combined to form a new numerical range.

[0011] <Catalyst manufacturing method> The method for producing a catalyst according to this embodiment is a method for producing a catalyst used in producing an α,β-unsaturated carboxylic acid by oxidizing an α,β-unsaturated aldehyde.

[0012] [catalyst] The catalyst obtained by the catalyst production method according to this embodiment is used when producing an α,β-unsaturated carboxylic acid by oxidizing an α,β-unsaturated aldehyde. From the viewpoint of improving the yield of the α,β-unsaturated carboxylic acid, the catalyst preferably has a composition represented by the following formula (II). Note that the catalyst may contain small amounts of elements not represented by the following formula (II): P a Mo b V c Cu d G e (NH4) f O g (II). In formula (II), P, Mo, V, Cu, NH4, and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively. G represents at least one element selected from the group consisting of alkali metals. a to g represent the molar ratio of each component, where when b = 12, a = 0.5 to 3, c = 0.01 to 3, d = 0.01 to 2, e = 0.01 to 3, and f = 0.01 to 10, and g represents the molar ratio of oxygen required to satisfy the valence of each component.

[0013] In the formula (II), from the viewpoint of improving the yield of α,β-unsaturated carboxylic acid, when b is 12, a is preferably 0.6 or more, more preferably 0.7 or more. Furthermore, a is preferably 2.5 or less, more preferably 2 or less. c is preferably 0.1 or more, more preferably 0.15 or more, and even more preferably 0.2 or more. Furthermore, c is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.5 or less. d is preferably 0.03 or more, more preferably 0.05 or more. e is preferably 0.05 or more, more preferably 0.1 or more. Furthermore, e is preferably 2.5 or less, more preferably 2 or less. Furthermore, f is preferably 9 or less, more preferably 8 or less.

[0014] In the formula (II), the molar ratio of each element is a value determined by analyzing a solution of the catalyst dissolved in ammonia water by ICP atomic emission spectrometry. The molar ratio of ammonium radicals is a value determined by analyzing the catalyst by the Kjeldahl method. In the present invention, the term "ammonium radicals" refers to ammonia (NH3) and ammonium ions (NH4 + ) is a general term for

[0015] [Catalyst manufacturing method] The method for producing a catalyst according to this embodiment includes the following steps (i) to (iii): (i) preparing a slurry (liquid A) containing molybdenum, phosphorus, and ammonium roots; (ii-1) mixing the solution A with a raw material compound containing an alkali metal to prepare a slurry (solution B1); (ii-2) mixing the B1 solution with a raw material compound containing an ammonium radical to prepare a slurry (B2 solution); and (iii) A step of drying the B2 liquid to obtain a catalyst.

[0016] In the catalyst production method according to this embodiment, the raw material compound containing an ammonium radical is added in portions so that the ratio of N1 to N2 (N1 / N2) is 0.15 to 0.6, where N1 is the number of moles of ammonium radical contained in the A solution and N2 is the number of moles of ammonium radical contained in the B2 solution. This allows for the production of a catalyst that has a high yield of α,β-unsaturated carboxylic acid and can suppress localized heat generation when used in the oxidation reaction of an α,β-unsaturated aldehyde. Each step will be described in detail below.

[0017] (Step (i)) In step (i), a slurry (liquid A) containing at least molybdenum, phosphorus, and ammonium radicals is prepared by mixing at least a raw material compound containing molybdenum, a raw material compound containing phosphorus, and a raw material compound containing ammonium radicals with a solvent. The slurry (liquid A) may be a solution. The preparation of liquid A is preferably carried out simply and conveniently by adding some or all of the raw material compounds of the elements constituting the catalyst to a solvent and stirring while heating. A solution, slurry, or sol of the raw material compounds of the elements constituting the catalyst may also be added to the solvent. When producing a catalyst having a composition represented by formula (II), it is preferable to prepare liquid A containing elements other than the G element contained in the composition represented by formula (II) in this step. That is, liquid A preferably contains molybdenum, phosphorus, vanadium, copper, and ammonium radicals. Examples of solvents include water, ethanol, and acetone, but water is preferred.

[0018] The raw material compounds used are not particularly limited, and nitrates, carbonates, bicarbonates, acetates, ammonium salts, sulfates, oxides, hydroxides, halides, oxoacids, or oxoacid salts of the elements constituting the catalyst can be used alone or in combination of two or more. Examples of molybdenum raw materials include ammonium paramolybdate, molybdenum trioxide, molybdic acid, and molybdenum chloride. Examples of phosphorus raw materials include phosphoric acid, phosphorus pentoxide, ammonium phosphate, and cesium phosphate. Examples of ammonium root raw materials include ammonium salts of each element, as well as ammonium bicarbonate, ammonium carbonate, ammonium nitrate, and aqueous ammonia. Examples of copper raw materials include copper sulfate, copper nitrate, copper oxide, copper carbonate, copper acetate, and copper chloride. Examples of vanadium raw materials include ammonium metavanadate, vanadium pentoxide, and vanadium chloride. These raw materials can be used alone or in combination of two or more.

[0019] In addition, when the ammonium salt of the element constituting the catalyst is used as the ammonium root raw material, the ammonium salt is also a raw material compound containing the ammonium root, and is also a raw material compound containing the element. In addition, when the ammonium root raw material contains the ammonium salt of the element constituting the catalyst, for example, the number of moles N1 of the ammonium root contained in the A solution is the number of moles of the ammonium root including the number of moles of the ammonium ion contained in the ammonium salt.

[0020] Furthermore, as the raw material compound containing molybdenum, phosphorus, and vanadium, a heteropolyacid containing at least one element selected from molybdenum, phosphorus, and vanadium may be used. Examples of heteropolyacids include phosphomolybdic acid, phosphovanadomolybdic acid, and silicomolybdic acid. These may be used alone or in combination of two or more.

[0021] When the number of moles of ammonium radicals contained in Solution A is N1 and the number of moles of ammonium radicals contained in Solution B2 (described later) is N2, the ratio N1 / N2 is 0.15 to 0.6. Specifically, in step (i), Solution A containing a portion of the ammonium radical raw material is first prepared. Subsequently, in steps (ii-1) and (ii-2) (described later), a raw material compound containing an alkali metal and a raw material compound containing the remaining ammonium radical are sequentially added to Solution A, thereby achieving a suitable degree of supersaturation of the heteropolyacid composite salt. As a result, a heteropolyacid composite salt suitable for producing α,β-unsaturated carboxylic acids is believed to be stably formed. The heteropolyacid composite salt refers to a salt in which an alkali metal salt and an ammonium salt of a heteropolyacid are combined in a specific ratio. The lower limit of N1 / N2 is preferably 0.2, and the upper limit of N1 / N2 is preferably 0.45, more preferably 0.4.

[0022] Furthermore, in the method for producing a catalyst according to this embodiment, from the viewpoint of the yield of α,β-unsaturated carboxylic acid, it is preferable to prepare the catalyst so as to satisfy at least one of the following formulas (I-1) and (I-2), and it is more preferable to prepare the catalyst so as to satisfy both the following formulas (I-1) and (I-2): n1=0.01~4.5 (I-1); m1=6~12 (I-2). In formula (I-1), n1 represents the molar ratio of ammonium radicals contained in the solution A when the molar ratio of molybdenum in the catalyst is 12, and in formula (I-2), m1 represents the molar ratio of molybdenum contained in the solution B1 when the molar ratio of molybdenum in the catalyst is 12. For example, when the catalyst has a composition represented by formula (II) above, m1 is 12.

[0023] Liquid A is preferably prepared by mixing at least a molybdenum-containing raw material compound, a phosphorus-containing raw material compound, and an ammonium radical-containing raw material compound with a solvent to form a mixture (solution or slurry) containing at least molybdenum, phosphorus, and ammonium radical, and then stirring and maintaining the mixture at a temperature of 80°C or higher for at least 1 hour. This allows for more stable formation of a heteropolyacid (salt) in Liquid A. Furthermore, in step (iii) described below, a catalyst having pores suitable for the production of an α,β-unsaturated carboxylic acid can be easily produced. The lower limit of the heating temperature is preferably 90°C, and the upper limit is preferably 130°C. The lower limit of the holding time is preferably 1.5 hours, more preferably 2 hours. The upper limit of the holding time is not particularly limited, but is usually 5 hours or less to shorten the time required for catalyst production.

[0024] (Process (ii-1)) In step (ii-1), the liquid A obtained in step (i) is mixed with a raw material compound containing an alkali metal to prepare a slurry (liquid B1). The slurry (liquid B1) may be a solution. The method for mixing the liquid A and the raw material compound containing an alkali metal is not particularly limited, but it is preferable to dissolve or suspend the raw material compound containing an alkali metal in a solvent to prepare a solution or slurry, and then mix the solution or slurry with liquid A. The solvent may be the same as the solvent used in preparing the liquid A.

[0025] As the alkali metal, it is preferable to use at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, more preferably at least one element selected from the group consisting of potassium and cesium, and even more preferably cesium. Examples of raw material compounds containing alkali metals include nitrates, carbonates, bicarbonates, hydroxides, sulfates, acetates, and chlorides of each alkali metal element. Among these, it is preferable to use carbonates or bicarbonates. One type of raw material compound containing an alkali metal may be used, or two or more types may be used in combination.

[0026] The temperature of the solution A to be mixed with the alkali metal-containing raw material compound is preferably 30° C. to 99° C., more preferably 70° C. or higher, from the viewpoint of suppressing local heat generation in the reaction for producing an α,β-unsaturated carboxylic acid using the obtained catalyst, thereby further improving the activity of the obtained catalyst.

[0027] (Step (ii-2)) In step (ii-2), the B1 solution obtained in step (ii-1) is mixed with a raw material compound containing an ammonium radical to prepare a slurry (B2 solution). The raw material compound containing an ammonium radical is preferably dissolved or suspended in a solvent to form a solution or slurry, and then the solution or slurry is mixed with B1 solution. The solvent may be the same as that used in preparing the A solution. The raw material compound containing an ammonium radical may be the same as the ammonium radical raw material described in step (i). The raw material compound containing an ammonium radical mixed in this step may be the same as or different from the raw material compound containing an ammonium radical mixed in step (i). The ratio of the raw material compound containing an ammonium radical selected from the group consisting of ammonium salts of the elements constituting the catalyst, ammonium bicarbonate, ammonium carbonate, ammonium nitrate, and aqueous ammonia to the total amount of the raw material compound containing an ammonium radical added in this step is preferably 30% by mass or more, more preferably 50% by mass or more, and may even be 100% by mass.

[0028] The temperature of the liquid B1 to be mixed with the raw material compound containing an ammonium radical is preferably 30°C to 99°C, more preferably 70°C or higher, from the viewpoint of suppressing local heat generation in the reaction for producing an α,β-unsaturated carboxylic acid using the resulting catalyst, thereby further improving the activity of the resulting catalyst.

[0029] In step (ii-2), it is preferable to prepare Liquid B2 by mixing Liquid B1 with a raw material compound containing an ammonium radical to obtain a mixture (solution or slurry) and stirring the mixture at a temperature of 90 to 99°C for 15 minutes or more. This promotes the dissolution and reprecipitation of the heteropolyacid salt, allowing the formation of a crystalline structure suitable for the production of an α,β-unsaturated carboxylic acid. From the viewpoint of promoting the dissolution and reprecipitation of the heteropolyacid salt, the heating temperature is more preferably 95°C or higher.

[0030] The pH of the solution B2 obtained in step (ii-2) is preferably 4 or less. This ensures stable formation of a Keggin-type heteropolyacid, which is a structure suitable for producing an α,β-unsaturated carboxylic acid. The pH of the solution B2 is more preferably 3.5 or less, and even more preferably 3 or less. The pH of the solution B2 can be adjusted by appropriately selecting the type and amount of the raw material compounds and by appropriately adding nitric acid, oxalic acid, or the like. The pH can be measured using, for example, a pH meter (trade name: D-21, manufactured by Horiba, Ltd.).

[0031] (Step (iii)) In step (iii), the B2 solution obtained in step (ii-2) is dried to obtain a catalyst. Examples of drying methods include drum drying, flash drying, evaporation to dryness, and spray drying. The drying temperature is preferably 120°C to 500°C, with a lower limit of 140°C and an upper limit of 350°C. Drying can be carried out until the B2 solution is dried to dryness. The water content of the obtained catalyst is preferably 0.1% by mass to 4.5% by mass. These drying conditions can be appropriately selected depending on the desired shape and size of the catalyst.

[0032] The catalyst obtained in step (iii) can be used for producing an α,β-unsaturated carboxylic acid. Furthermore, by subjecting the catalyst to molding and calcination, as described below, the catalytic performance is improved, which is preferable. In the present invention, the term "catalyst" collectively refers to the catalyst obtained in step (iii), as well as the molded catalyst and the calcined catalyst.

[0033] (molding process) In the molding step, the catalyst obtained in the step (iii) is crushed as necessary and then molded. The molding step may be performed after the calcination step described below. The molding method is not particularly limited, and known dry or wet molding methods can be applied. Examples of molding methods include tableting, extrusion, pressure molding, and tumbling granulation. The shape of the molded product is not particularly limited, and examples include any shape such as spherical granules, rings, cylindrical pellets, stars, and granules crushed and classified after molding. The catalyst preferably has a diameter of 0.1 mm to 10 mm. A catalyst diameter of 0.1 mm or more can reduce pressure loss within the reaction tube. Furthermore, a catalyst diameter of 10 mm or less can further improve catalytic activity. When molding the catalyst, the catalyst may be supported on a carrier. If necessary, known additives such as graphite or talc, or known organic or inorganic binders, may be added to the catalyst before molding.

[0034] (Firing process) From the viewpoint of the yield of α,β-unsaturated carboxylic acid, it is preferable to calcinate the catalyst obtained in the step (iii) or the catalyst obtained in the molding step. The calcination conditions are not particularly limited, but can be carried out, for example, by heat treatment under a flow of at least one of an oxygen-containing gas such as air and an inert gas. Calcination is preferably carried out under a flow of an oxygen-containing gas. The term "inert gas" refers to a gas that does not reduce catalytic activity, and examples include nitrogen, carbon dioxide, helium, and argon. These gases may be used alone or in combination of two or more. The calcination temperature is preferably 200°C to 500°C, with a lower limit of 300°C and an upper limit of 450°C. The lower limit of the calcination time is preferably 0.5 hours, and more preferably 1 hour. The upper limit of the calcination time is preferably 40 hours.

[0035] <Method of producing α,β-unsaturated carboxylic acid> In the method for producing an α,β-unsaturated carboxylic acid according to this embodiment, an α,β-unsaturated aldehyde is oxidized in the presence of a catalyst produced by the method for producing a catalyst according to this embodiment, thereby producing an α,β-unsaturated carboxylic acid in high yield.

[0036] Examples of α,β-unsaturated aldehydes include (meth)acrolein, crotonaldehyde (β-methylacrolein), and cinnamaldehyde (β-phenylacrolein). Among these, (meth)acrolein is preferred, and methacrolein is more preferred, from the viewpoint of the yield of the target product. The resulting α,β-unsaturated carboxylic acid is an α,β-unsaturated carboxylic acid in which the aldehyde group of the α,β-unsaturated aldehyde is converted to a carboxyl group. Specifically, when the α,β-unsaturated aldehyde is (meth)acrolein, (meth)acrylic acid is obtained. Note that "(meth)acrolein" refers to acrolein and methacrolein, and "(meth)acrylic acid" refers to acrylic acid and methacrylic acid.

[0037] Hereinafter, as a representative example, a method for producing methacrylic acid by oxidizing methacrolein in the presence of a catalyst produced by the method according to this embodiment will be described. In this method, methacrylic acid is produced by contacting a raw material gas containing methacrolein and oxygen with the catalyst obtained by the method according to this embodiment in a reactor. A fixed-bed reactor can be used as the reactor. The catalyst is packed into reaction tubes provided in the reactor, and the raw material gas is supplied to the reaction tubes to carry out the oxidation reaction. The catalyst layer may be a single layer, or multiple catalysts with different activities may be packed in separate layers. In addition, the catalyst may be diluted with an inert carrier and packed to control the activity.

[0038] The concentration of methacrolein in the raw material gas is not particularly limited, but is preferably 1% by volume to 20% by volume, with the lower limit more preferably 3% by volume and the upper limit more preferably 10% by volume. The raw material methacrolein may contain small amounts of impurities such as lower saturated aldehydes that do not substantially affect the reaction. The concentration of oxygen in the raw material gas is preferably 0.4 mol to 4 mol per mol of methacrolein, with the lower limit more preferably 0.5 mol and the upper limit more preferably 3 mol. From an economical viewpoint, air is preferred as the oxygen source. If necessary, a gas enriched with oxygen by adding pure oxygen to air may be used.

[0039] The raw material gas may be prepared by diluting methacrolein and oxygen (or an oxygen source) 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% by volume to 50% by volume, with the lower limit being more preferably 1% by volume and the upper limit being more preferably 40% by volume.

[0040] The contact time between the raw material gas and the catalyst is preferably 0.5 to 15 seconds. The reaction pressure is preferably 0.1 MPa (G) to 1 MPa (G), where (G) means gauge pressure. The reaction temperature is preferably 200 to 450°C, with the lower limit more preferably 250°C and the upper limit more preferably 400°C.

[0041] <Method of producing α,β-unsaturated carboxylic acid ester> In the method for producing an α,β-unsaturated carboxylic acid ester according to this embodiment, the α,β-unsaturated carboxylic acid produced by the method according to this embodiment is esterified. According to this method, an α,β-unsaturated carboxylic acid ester can be produced using an α,β-unsaturated carboxylic acid obtained by oxidation of an α,β-unsaturated aldehyde.

[0042] The alcohol to be reacted with the α,β-unsaturated carboxylic acid is not particularly limited, and examples thereof include methanol, ethanol, propanol, isopropanol, n-butanol, and isobutanol. Examples of the resulting α,β-unsaturated carboxylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, and isobutyl (meth)acrylate. The esterification reaction can be carried out in the presence of an acid catalyst such as a sulfonic acid-type cation exchange resin. The reaction temperature is preferably 50°C to 200°C. [Example]

[0043] 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. In the examples and comparative examples, "parts" means parts by mass. The ammonium carbonate used in the examples and comparative examples has an ammonium root content of 32.3 mass%.

[0044] (Analysis of raw gas and products) The raw material gas and the product were analyzed by gas chromatography (details are shown in Table 1). From the results of gas chromatography, the yield of methacrylic acid was calculated using the following formula: Yield of methacrylic acid (%) = (P / F) × 100. In the formula, F represents the number of moles of methacrolein supplied per unit time, and P represents the number of moles of methacrylic acid produced per unit time.

[0045] [Table 1]

[0046] [Example 1] (Step (i)) A slurry was prepared by adding 100 parts of molybdenum trioxide to 400 parts of pure water. Subsequently, 2.71 parts of ammonium metavanadate, an aqueous solution prepared by diluting 10.68 parts of an 85% by mass aqueous phosphoric acid solution with 14.4 parts of pure water, an aqueous solution prepared by dissolving 1.4 parts of copper (II) nitrate trihydrate in 3 parts of pure water, and an aqueous solution prepared by dissolving 0.8 parts of ammonium carbonate in 2.41 parts of pure water (hereinafter referred to as "aqueous solution 1 containing ammonium roots") were added to the slurry. The resulting mixture (slurry) was then heated to 95°C with stirring, and stirred for 2 hours while maintaining the temperature at 95°C to prepare Solution A. (Process (ii-1)) Next, while maintaining the temperature of the obtained solution A at 95°C and stirring, an aqueous solution prepared by dissolving 11.23 parts of cesium hydrogen carbonate in 20 parts of pure water was added dropwise to the solution A, and the mixture was stirred for 15 minutes to prepare solution B1. (Step (ii-2)) Next, while maintaining the temperature of the obtained B1 liquid at 95°C and stirring, an aqueous solution of 8.38 parts of ammonium carbonate dissolved in 25.13 parts of pure water (hereinafter referred to as "aqueous solution 2 containing ammonium root") was added dropwise, and the mixture was stirred for 15 minutes to prepare B2 liquid. (Step (iii)) Next, the obtained B2 liquid was heated with steam at 140° C. to evaporate and dry, thereby obtaining a catalyst having the composition represented by the above formula (II).

[0047] Table 2 shows the ratio N1 / N2 of the number of moles of ammonium roots in Solution A (N1) to the number of moles of ammonium roots in Solution B2 (N2), as well as the molar ratio n1 of ammonium roots in Solution A and the molar ratio m1 of molybdenum in Solution B1 when the molar ratio of molybdenum in the catalyst is 12. The ammonium metavanadate used as the vanadium source is also an ammonium root source. As mentioned above, the ammonium root content in ammonium carbonate was assumed to be 32.3% by mass, and the number of moles of ammonium roots was calculated.

[0048] Subsequently, the obtained catalyst was pressure-molded and then pulverized, and calcined at 380° C. for 5 hours in an air stream to obtain a calcined catalyst. The calcined catalyst was packed into a reaction tube equipped with a fixed-bed reactor, and a feed gas consisting of 5% methacrolein by volume, 10% oxygen by volume, 10% steam by volume, and 75% nitrogen by volume was passed through the reaction tube for a contact time of 3.5 seconds to carry out the oxidation reaction of methacrolein. The reaction was carried out at atmospheric pressure and a reaction temperature of 300°C. The results are shown in Table 2.

[0049] [Example 2] Solution A was prepared in the same manner as in Example 1, except that an aqueous solution prepared by dissolving 1.85 parts of ammonium carbonate in 5.55 parts of pure water was used as aqueous solution 1 containing ammonium roots. Next, using the obtained solution A, solution B1 was prepared in the same manner as in Example 1. Next, using the obtained B1 solution, B2 solution was prepared in the same manner as in Example 1, except that an aqueous solution containing 7.33 parts of ammonium carbonate dissolved in 21.99 parts of pure water was added dropwise as aqueous solution 2 containing ammonium roots. The resulting B2 solution was then used to prepare a catalyst in the same manner as in Example 1. Table 2 shows the values ​​of N1 / N2, n1, and m1 in the catalyst production.

[0050] Subsequently, the obtained catalyst was used to obtain a calcined catalyst in the same manner as in Example 1. Then, the obtained calcined catalyst was used to carry out an oxidation reaction of methacrolein in the same manner as in Example 1. The results are shown in Table 2.

[0051] [Example 3] Solution A was prepared in the same manner as in Example 1, except that an aqueous solution containing ammonium radicals 1 was prepared by dissolving 2.90 parts of ammonium carbonate in 8.69 parts of pure water. Next, using the obtained solution A, solution B1 was prepared in the same manner as in Example 1. Next, using the obtained B1 solution, B2 solution was prepared in the same manner as in Example 1, except that an aqueous solution containing 6.28 parts of ammonium carbonate in 18.85 parts of pure water was added dropwise as aqueous solution 2 containing ammonium roots. The resulting B2 solution was then used to prepare a catalyst in the same manner as in Example 1. Table 2 shows the values ​​of N1 / N2, n1, and m1 in the catalyst production.

[0052] Subsequently, the obtained catalyst was used to obtain a calcined catalyst in the same manner as in Example 1. Then, the obtained calcined catalyst was used to carry out an oxidation reaction of methacrolein in the same manner as in Example 1. The results are shown in Table 2.

[0053] [Example 4] Solution A was prepared in the same manner as in Example 1, except that an aqueous solution prepared by dissolving 4.99 parts of ammonium carbonate in 14.97 parts of pure water was used as aqueous solution 1 containing ammonium roots. Next, using the obtained solution A, solution B1 was prepared in the same manner as in Example 1. Next, using the obtained B1 solution, B2 solution was prepared in the same manner as in Example 1, except that an aqueous solution containing 4.19 parts of ammonium carbonate in 12.56 parts of pure water was added dropwise as aqueous solution 2 containing ammonium roots. The resulting B2 solution was then used to prepare a catalyst in the same manner as in Example 1. Table 2 shows the values ​​of N1 / N2, n1, and m1 in the catalyst production.

[0054] Subsequently, the obtained catalyst was used to obtain a calcined catalyst in the same manner as in Example 1. Then, the obtained calcined catalyst was used to carry out an oxidation reaction of methacrolein in the same manner as in Example 1. The results are shown in Table 2.

[0055] [Comparative Example 1] Solution A was prepared in the same manner as in Example 1, except that an aqueous solution prepared by dissolving 9.18 parts of ammonium carbonate in 27.54 parts of pure water was used as aqueous solution 1 containing ammonium roots. Next, using the obtained solution A, solution B1 was prepared in the same manner as in Example 1. Next, without carrying out step (ii-2), the obtained B1 liquid was used as B2 liquid as it was to obtain a catalyst in the same manner as in Example 1. Table 2 shows the values ​​of N1 / N2, n1, and m1 in the catalyst production.

[0056] Subsequently, the obtained catalyst was used to obtain a calcined catalyst in the same manner as in Example 1. Then, the obtained calcined catalyst was used to carry out an oxidation reaction of methacrolein in the same manner as in Example 1. The results are shown in Table 2.

[0057] [Table 2]

[0058] As shown in Table 2, it was found that the methods of Examples 1 to 4, which include the steps (i) to (iii) and have an N1 / N2 ratio within the range specified by the present invention, can provide catalysts capable of producing methacrylic acid in a higher yield than the method of Comparative Example 1, in which the N1 / N2 ratio is outside the range. Note that methacrylic acid esters can be obtained by esterifying the methacrylic acid obtained in this example. [Industrial Applicability]

[0059] According to the present invention, it is possible to produce an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde in high yield, and it is possible to provide a catalyst that can suppress local heat generation during the production of an α,β-unsaturated carboxylic acid, and this is industrially useful.

Claims

1. A method for producing a catalyst used in producing an α,β-unsaturated carboxylic acid by oxidizing an α,β-unsaturated aldehyde, comprising the steps of: (i) preparing a slurry (liquid A) containing molybdenum, phosphorus, and ammonium radicals; (ii-1) mixing the solution A with a raw material compound containing an alkali metal to prepare a slurry (solution B1); (ii-2) mixing the B1 solution with a raw material compound containing an ammonium radical to prepare a slurry (B2 solution); (iii) drying the B2 solution to obtain a catalyst; and When the number of moles of ammonium radicals contained in the A solution is N1 and the number of moles of ammonium radicals contained in the B2 solution is N2, N1 / N2 is 0.15 to 0.

6.

2. The method for producing a catalyst according to claim 1, wherein the N1 / N2 ratio is 0.2 to 0.

45.

3. 2. The method for producing a catalyst according to claim 1, wherein in the step (i), the solution A is prepared by mixing a raw material compound containing molybdenum, a raw material compound containing phosphorus, and a raw material compound containing an ammonium radical with a solvent, and maintaining the mixture with stirring at a temperature of 80°C or higher for 1 hour or more.

4. A method for producing the catalyst according to claim 1, which satisfies at least one of the following formulas (I-1) and (I-2): n1=0.01~4.5 (I-1); m1=6~12 (I-2), In formula (I-1), n1 represents the molar ratio of ammonium radicals contained in the A solution when the molar ratio of molybdenum in the catalyst is 12, and in formula (I-2), m1 represents the molar ratio of molybdenum contained in the B1 solution when the molar ratio of molybdenum in the catalyst is 12.

5. The method for producing a catalyst according to claim 4, wherein both of the formula (I-1) and the formula (I-2) are satisfied.

6. 2. The method for producing a catalyst according to claim 1, wherein the catalyst has a composition represented by the following formula (II): P ａ Mỏ ｂ V ｃ Cổ ｄ G ｅ (NH) ４ ) ｆ O ｇ (II) In formula (II), P, Mo, V, Cu, NH ４ and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively; G represents at least one element selected from the group consisting of alkali metals; a to g represent the molar ratios of each component, such that when b = 12, a = 0.5 to 3, c = 0.01 to 3, d = 0.01 to 2, e = 0.01 to 3, and f = 0.01 to 10; and g represents the molar ratio of oxygen necessary to satisfy the valence of each component.

7. 2. The method for producing a catalyst according to claim 1, wherein in the step (ii-1), the temperature of the solution A to be mixed with the raw material compound containing an alkali metal is 30°C to 99°C.

8. 2. The method for producing a catalyst according to claim 1, wherein in the step (ii-2), the temperature of the B1 solution mixed with the raw material compound containing an ammonium radical is 30°C to 99°C.

9. A method for producing an α,β-unsaturated carboxylic acid, which comprises oxidizing an α,β-unsaturated aldehyde in the presence of a catalyst produced by the method according to any one of claims 1 to 8.

10. A method for producing an α,β-unsaturated carboxylic acid ester, which comprises esterifying the α,β-unsaturated carboxylic acid produced by the method according to claim 9.

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