Method for producing catalyst for synthesizing unsaturated carboxylic acid and catalyst for synthesizing unsaturated carboxylic acid

Abstract

To provide a method for producing a catalyst for synthesizing an unsaturated carboxylic acid and a catalyst capable of increasing selectivity and yield of an unsaturated carboxylic acid obtained even at low reaction temperatures.SOLUTION: There is provided a method for producing a catalyst for synthesizing an unsaturated carboxylic acid, which comprises: a solution preparation step of dissolving and / or dispersing a supply source compound of a plurality of catalyst component elements containing molybdenum and a sulfur-containing inorganic compound in an aqueous liquid to obtain a starting raw material mixed solution; a first powdering step of drying the starting raw material mixed solution to obtain a first powder; a drying step of heat-treating the first powder to obtain a dried product; and a molding step of forming the dried product into a second powder, followed by forming into a catalyst precursor, wherein the ratio of the difference between the loss on ignition of the second powder at 500°C and the loss on ignition of the second powder at 250°C to the difference between the loss on ignition of the first powder at 500°C and the loss on ignition of the first powder at 250°C is in the range of 0.4% or more and 45% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a catalyst for unsaturated carboxylic acid synthesis and a catalyst for unsaturated carboxylic acid synthesis.

Background Art

[0002] Catalysts used in the production of acrylic acid by gas-phase catalytic oxidation of acrolein have been studied for a long time (Patent Documents 1 to 3). For example, Patent Document 3 discloses a catalyst having a composition of a catalytic active component represented by the formula (1) (Mo) 12 (V) a (W) b (Cu) c (Sb) d (X) e (Y) f (Z) g (O) h (1) (In the formula, Mo, V, W, Cu, Sb, and O represent molybdenum, vanadium, tungsten, copper, antimony, and oxygen, respectively. X represents at least one element selected from the group consisting of an alkali metal and thallium. Y represents at least one element selected from the group consisting of magnesium, calcium, strontium, barium, and zinc. Z represents at least one element selected from the group consisting of niobium, cerium, tin, chromium, manganese, iron, cobalt, samarium, germanium, titanium, and arsenic. Also, a, b, c, d, e, f, g, and h represent the atomic ratios of the respective elements. With respect to 12 molybdenum atoms, a is 0 < a ≤ 10, b is 0 ≤ b ≤ 10, c is 0 < c ≤ 6, d is 0 < d ≤ 10, e is 0 ≤ e ≤ 0.5, f is 0 ≤ f ≤ 1, g is 0 ≤ g < 6. Also, h is the number of oxygen atoms necessary to satisfy the valence of the respective components.) A catalyst having the composition of the catalytic active component is disclosed, and in the 2θ value (θ represents the diffraction angle in X-ray diffraction) of X-ray diffraction using the Kα line of copper for the catalytic active component, a catalyst having the maximum peak intensity of 22.2 ± 0.3 degrees is disclosed.

Prior Art Documents

Patent Documents

[0003] [Patent Document 1] Patent No. 3786297 [Patent Document 2] Special Publication No. 41-1775 [Patent Document 3] Special Publication No. 44-12129 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the catalyst for synthesizing unsaturated carboxylic acid is produced, for example, by the following method. Figure 1 shows an example of a production scheme for a catalyst for synthesizing unsaturated carboxylic acid, in which (1) is a starting material and (8) is a catalyst for synthesizing unsaturated carboxylic acid. In Figure 1, (1) the starting material undergoes (2) a liquid preparation step, (3) a first powdering step, (4) a drying step, (5) a second powdering step, (6) a molding step, and (7) a calcination step, and (8) a catalyst for synthesizing unsaturated carboxylic acid is obtained. Here, when synthesizing an unsaturated carboxylic acid such as acrylic acid or methacrylic acid from an unsaturated aldehyde such as acrolein, depending on the type of catalyst for synthesizing the unsaturated carboxylic acid, unless the reaction temperature is increased, the unsaturated aldehyde may not be sufficiently converted, or the selectivity and yield of the resulting unsaturated carboxylic acid may be low. The present invention aims to solve the above problems, and aims to provide a method for producing a catalyst for synthesizing an unsaturated carboxylic acid, which is used when synthesizing an unsaturated carboxylic acid from an unsaturated aldehyde, and which is capable of sufficiently converting an unsaturated aldehyde even at a low reaction temperature, thereby increasing the selectivity and yield of the resulting unsaturated carboxylic acid, and a catalyst for synthesizing an unsaturated carboxylic acid. [Means for solving the problem]

[0005] In light of the above-mentioned problems, the present inventors have conducted research and found that the above-mentioned problems can be solved by using a sulfur-containing inorganic compound in the production of a catalyst for synthesizing unsaturated carboxylic acids, and by using a first powder that decomposes at about 500°C in the first powdering step. Specifically, the above problems were solved by the following means. [1] A liquid preparation step of dissolving and / or dispersing a source compound of a plurality of catalyst component elements including molybdenum and a sulfur-containing inorganic compound in an aqueous liquid to obtain a starting material mixture; a first powdering step of drying the starting material mixture to obtain a first powder; A drying step of obtaining a dried product by heat-treating the first powder; and A molding step of forming the dried product into a second powder and / or obtaining a second powder from the dried product, supporting the second powder on a granular support, and / or molding the second powder into a ring shape to form a catalyst precursor. A method for producing a catalyst for synthesizing an unsaturated carboxylic acid, comprising: A method for producing a catalyst for synthesizing unsaturated carboxylic acids, wherein the ratio of the difference between the ignition loss of the second powder at 500°C and the ignition loss of the second powder at 250°C to the difference between the ignition loss of the first powder at 500°C and the ignition loss of the first powder at 250°C is within the range of 0.4% or more and 45% or less. Burning loss (%)X=[(W 0 -W 1 ) / W 0 ] x 100 (W 0 : mass of powder before heating (g), W 1 : mass of powder after heating (g) Burning weight loss difference Y=X 500 -X 250 (X 500 : Ignition loss at 500℃, X 250 : Ignition loss at 250℃) Burning weight loss difference ratio Z = (Y 2 / Y 1 ) x 100 (Y 1 : Ignition loss difference of the first powder, Y 2: (Difference in loss on ignition of the second powder) [2] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to [1], wherein the sulfur-containing inorganic compound does not contain copper sulfate. [3] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to [1] or [2], wherein the sulfur-containing inorganic compound is added after at least a part of the source compound is added to the aqueous liquid. [4] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of [1] to [3], wherein the sulfur-containing inorganic compound contains a sulfate. [5] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of [1] to [4], wherein the composition formula of the catalyst component elements of the catalyst for synthesizing an unsaturated carboxylic acid is represented by formula (1). Mo 12 V a X b Cu c Y d Sb e Z f Si g C h O i (1) (In formula (1), X represents Nb and / or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and Z represents at least one element selected from the group consisting of Fe, Co, Ni, and Bi. a to i represent the atomic ratios of the respective elements, and are in the ranges of 0 < a ≤ 12, 0 ≤ b ≤ 12, 0 < c ≤ 12, 0 ≤ d ≤ 8, 0 ≤ e ≤ 500, 0 ≤ f ≤ 500, 0 ≤ g ≤ 500, 0 ≤ h ≤ 500, and i is a value that satisfies the oxidation state of the other elements.) [6] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of [1] to [5], wherein the heat treatment in the drying step is performed in an atmosphere with an oxygen concentration of 10% or less. [7] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of [1] to [6], wherein the heat treatment temperature in the heat treatment is 330°C or higher and 450°C or lower. [8] The sulfur-containing inorganic compound does not contain copper sulfate and contains a sulfate, After adding at least a part of the supply source compound to the aqueous liquid, the sulfur-containing inorganic compound is added. The composition formula of the catalyst component elements of the catalyst for synthesizing unsaturated carboxylic acid is represented by the formula (1). The heat treatment in the drying step is performed in an atmosphere with an oxygen concentration of 10% or less. The heat treatment temperature in the heat treatment is 330 ° C or higher and 450 ° C or lower. The method for producing a catalyst for synthesizing unsaturated carboxylic acid according to any one of [1] to [7]. Mo 12 V a X b Cu c Y d Sb e Z f Si g C h O i (1) (In the formula (1), X represents Nb and / or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and Z represents at least one element selected from the group consisting of Fe, Co, Ni, and Bi. a to i represent the atomic ratios of the respective elements, and are in the ranges of 0 < a ≤ 12, 0 ≤ b ≤ 12, 0 < c ≤ 12, 0 ≤ d ≤ 8, 0 ≤ e ≤ 500, 0 ≤ f ≤ 500, 0 ≤ g ≤ 500, 0 ≤ h ≤ 500, and i is a value that satisfies the oxidation state of other elements.) [9] The catalyst for synthesizing unsaturated carboxylic acid is a catalyst for synthesizing acrylic acid. The method for producing a catalyst for synthesizing unsaturated carboxylic acid according to any one of [1] to [8].

[10] A catalyst for synthesizing unsaturated carboxylic acid obtained by the method for producing a catalyst for synthesizing unsaturated carboxylic acid according to any one of [1] to [8].

Advantages of the Invention

[0006] According to the present invention, there is provided a method for producing a catalyst for synthesizing unsaturated carboxylic acid used for synthesizing unsaturated carboxylic acid from unsaturated aldehyde, which can sufficiently convert unsaturated aldehyde even at a low reaction temperature and can increase the selectivity and yield of the obtained unsaturated carboxylic acid, and a catalyst for synthesizing unsaturated carboxylic acid. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 shows an example of a production scheme for a catalyst for synthesizing an unsaturated carboxylic acid. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present invention") will be described in detail. Note that the present invention described below is an example for explaining the present invention, and the present invention is not limited to the following description. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as upper and lower limits. "A to B" means that the range is A or greater and B or less. In addition, any combination of the upper and lower limit values ​​of the numerical values ​​in this specification is an example of the present invention.

[0009] In this specification, "% by mass" indicates the content of a given component in a total amount of 100% by mass. In this specification, various physical properties and characteristic values ​​are those at 23°C unless otherwise specified.

[0010] As used herein, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps, as long as the intended effect of the step is achieved. All steps described herein can be performed in any suitable order unless otherwise specified in the specification or clearly contradicted by the context. If the measurement methods, etc. described in the standards shown in this specification change from year to year, they will be based on the standards in effect as of January 1, 2024, unless otherwise specified. If the measurement methods, etc. described in the standards shown in this specification are abolished as of January 1, 2024, they will be based on the standards in effect at the time of abolition.

[0011] In this specification, unless otherwise specified, the term "catalyst" refers to a catalyst for synthesizing an unsaturated carboxylic acid.

[0012] The method for producing a catalyst for synthesizing unsaturated carboxylic acids of the present invention includes a liquid preparation step in which a source compound of multiple catalyst component elements, including molybdenum, and a sulfur-containing inorganic compound are dissolved and / or dispersed in an aqueous liquid to obtain a starting material mixture, a first powdering step in which the starting material mixture is dried to obtain a first powder, a drying step in which the first powder is heat-treated to obtain a dried product, and a molding step in which the dried product is converted into a second powder and / or the second powder is obtained from the dried product, and the second powder is supported on a granular carrier and / or molded into a ring shape to obtain a catalyst precursor, characterized in that the ratio of the difference between the ignition loss of the second powder at 500°C and the ignition loss of the second powder at 250°C to the difference between the ignition loss of the first powder at 500°C and the ignition loss of the first powder at 250°C is within the range of 0.4% to 45%. Burning loss (%)X=[(W 0 -W 1 ) / W 0 ] x 100 (W 0 : mass of powder before heating (g), W 1 : mass of powder after heating (g) Burning weight loss difference Y=X 500 -X 250 (X 500 : Ignition loss at 500℃, X 250 : Ignition loss at 250℃) Burning weight loss difference ratio Z = (Y 2 / Y 1 ) x 100 (Y 1 : Ignition loss difference of the first powder, Y 2 : Second powder burn loss difference)

[0013] By adopting such a configuration, it is possible to provide a catalyst for synthesizing an unsaturated carboxylic acid, which is used when synthesizing an unsaturated carboxylic acid from an unsaturated aldehyde, and which can sufficiently convert the unsaturated aldehyde even at a low reaction temperature, thereby increasing the selectivity and yield of the resulting unsaturated carboxylic acid.

[0014] In the catalyst manufacturing process for synthesizing unsaturated carboxylic acids, it is desirable to reduce the source compounds of multiple catalyst component elements, including molybdenum, contained in the starting materials at some stage. Previously, methods such as (6) blending a reducing agent with the binder in the molding process and (7) removing oxygen and reducing the catalyst in the calcination process were used. However, this method sometimes caused cracks in the catalyst or distortion of the catalyst's crystalline structure during reduction. As a result, unless the reaction temperature was raised, the unsaturated aldehyde was not sufficiently converted, and the selectivity and yield of the resulting unsaturated carboxylic acid were sometimes low.

[0015] In contrast, in the present invention, a sulfur-containing inorganic compound is used in the production of a catalyst for synthesizing unsaturated carboxylic acids, and the ratio of the difference between the ignition loss of the second powder at 500°C and the ignition loss of the second powder at 250°C to the difference between the ignition loss of the first powder at 500°C and the ignition loss of the first powder at 250°C is adjusted to be within the range of 0.4% or more and 45% or less. Sulfur-containing inorganic compounds (especially ammonium sulfate) typically decompose at about 500° C. and require oxygen for decomposition. In this embodiment, a catalyst component element supply source compound and a sulfur-containing inorganic compound are mixed and powdered, and the sulfur-containing inorganic compound decomposes the resulting powder and extracts oxygen, thereby reducing the supply source compound. That is, the first powder has a large difference between the ignition loss at 500°C and the ignition loss at 250°C. In contrast, the second powder, which has undergone the drying step (4), has a small difference between the ignition loss at 500°C and the ignition loss at 250°C. This means that the reduction reaction proceeds effectively in the drying step (4), and the crystalline structure is maintained in the state of the second powder. As a result, it is presumed that the catalyst obtained by the production method of the present invention can sufficiently convert unsaturated aldehydes even at low reaction temperatures, and can increase the selectivity and yield of the resulting unsaturated carboxylic acid, whereas conventionally, cracks may occur in the catalyst or the crystal structure of the catalyst may be distorted during the calcination step (7).

[0016] As described above, the ratio of the difference between the ignition loss of the second powder at 500°C and the ignition loss of the second powder at 250°C to the difference between the ignition loss of the first powder at 500°C and the ignition loss of the first powder at 250°C is in the range of 0.4% or more and 45% or less, preferably 0.5% or more, more preferably 0.8% or more, even more preferably 1.0% or more, even more preferably 1.5% or more, still more preferably 3% or more, and preferably 40% or less, more preferably 35% or less, even more preferably 30% or less, still more preferably 25% or less, and even more preferably 20% or less. The upper and lower limits of the ratio of the difference from the ignition loss can be arbitrarily combined, and are preferably 0.5% or more and 40% or less, more preferably 0.8% or more and 35% or less, even more preferably 1.0% or more and 30% or less, even more preferably 1.5% or more and 25% or less, and even more preferably 3% or more and 20% or less.

[0017] Hereinafter, the embodiments of the present invention will be described in detail in the order of (1) to (8) shown in FIG. 1. However, the explanation of the constituent elements described below is an example of an embodiment of the present invention, and the present invention is not limited to these contents. Unless otherwise specified, in the method for producing a catalyst for synthesizing an unsaturated carboxylic acid of the present invention, steps (2) to (7) are performed in the order mentioned above. However, it goes without saying that not all steps (2) to (7) are essential in the method for producing a catalyst of the present invention.

[0018] (1) Starting materials In the present invention, starting materials include a supply source compound for multiple catalyst component elements including molybdenum, a sulfur-containing inorganic compound, and an aqueous liquid. Furthermore, other components may be used within the scope of the present invention. Details of these components are described below.

[0019] [Source compounds of multiple catalyst component elements including molybdenum] The starting materials of the present invention include source compounds of multiple catalyst component elements, including molybdenum, which comprise the metal components that make up the catalyst. The source compound of the molybdenum-containing catalyst component elements essentially contains molybdenum (Mo), oxygen, and at least one selected from the group consisting of transition metals, post-transition metals, alkaline earth metals, and metalloids, and is preferably a compound of molybdenum (Mo) and oxygen (O), carbon (C), vanadium (V), niobium (Nb), tungsten (W), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), iron (Fe), cobalt (Co), nickel (Ni), bismuth (Bi), copper (Cu), antimony (Sb), thallium (Tl), cerium (Ce), tin (Sn), chromium (Cr), samarium (Sm), germanium (Ge), and It is more preferable that the alloy contains at least one selected from the group consisting of titanium (Ti), and it is even more preferable that the alloy contains at least one selected from the group consisting of molybdenum (Mo), oxygen (O), and carbon (C), vanadium (V), niobium (Nb), tungsten (W), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), iron (Fe), cobalt (Co), nickel (Ni), and bismuth (Bi), and it is even more preferable that the alloy contains at least one selected from the group consisting of molybdenum (Mo), oxygen (O), and vanadium (V), tungsten (W), copper (Cu), and antimony (Sb).

[0020] The supply source compounds of the above-mentioned catalyst component elements may be the catalyst component elements alone, but are usually blended in the form of compounds containing the catalyst component elements such as oxides or metal ions (cations). When compounded in the form of a metal ion (cation), the anion that pairs with the metal ion is also included. Such anions include NO3 - , SO4 2- , CO3 2- , O.H. - Examples include: For example, molybdenum is supplied as ammonium paramolybdate, molybdenum trioxide, molybdic acid, ammonium phosphomolybdate, phosphomolybdic acid or its salts, vanadium is supplied as ammonium vanadate, ammonium metavanadate, vanadium pentoxide, vanadium oxalate, vanadium sulfate or its salts, tungsten is supplied as ammonium paratungstate, tungstic acid or its salts, etc.

[0021] In the present invention, the composition formula of the catalyst component elements of the catalyst for unsaturated carboxylic acid synthesis is preferably represented by the formula (1). Mo 12 V a X b Cu c Y d Sb e Z f Si g C h O i (1) (In the formula (1), X represents Nb and / or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba and Zn, Z represents at least one element selected from the group consisting of Fe, Co, Ni and Bi. a to i represent the atomic ratios of the respective elements, and are in the ranges of 0 < a ≦ 12, 0 ≦ b ≦ 12, 0 ≦ c ≦ 12, 0 ≦ d ≦ 8, 0 ≦ e ≦ 500, 0 ≦ f ≦ 500, 0 ≦ g ≦ 500, 0 ≦ h ≦ 500, and i is a value that satisfies the oxidation state of other elements.)

[0022] [Sulfur-containing inorganic compound] The starting material of the present invention contains a sulfur-containing inorganic compound. The sulfur-containing inorganic compound is presumed to play a role in reducing the source compound. That is, it is presumed that the sulfur-containing inorganic compound decomposes in the (4) drying step described later, and at that time, it reduces the source compound of the catalyst component element. In the present invention, it is preferable that the sulfur-containing inorganic compound does not contain copper sulfate. Although copper sulfate can also be a source compound of the catalyst component element, when copper sulfate is blended as the sulfur-containing inorganic compound, a desired amount of sulfur source cannot be supplied. Therefore, it is more preferable that the sulfur-containing inorganic compound in the present invention does not contain any catalyst component element.

[0023] The sulfur-containing inorganic compound is preferably sulfuric acid, sulfates, sulfurous acid, sulfites, thiosulfuric acid, or thiosulfates, more preferably sulfates, and even more preferably ammonium sulfate (hereinafter sometimes referred to as "ammonium sulfate").

[0024] In the present invention, the amount of the sulfur-containing inorganic compound added to the aqueous liquid is preferably 0.1 to 5.0 molar equivalents of sulfur atoms relative to 12 molar equivalents of molybdenum atoms in the source compound added to the aqueous liquid. By adjusting the amount to be below the upper and lower limits, high conversion and high selectivity for producing unsaturated carboxylic acids tend to be achieved even at low reaction temperatures. The amount of the sulfur-containing inorganic compound added is preferably 0.2 or more molar equivalents of sulfur atoms relative to 12 molar equivalents of molybdenum atoms in the source compound, more preferably 0.3 or more molar equivalents, even more preferably 0.4 or more molar equivalents, more preferably 4.9 or less molar equivalents, even more preferably 4.8 or less molar equivalents, even more preferably 4.7 or less molar equivalents, even more preferably 4.6 or less molar equivalents, and even more preferably 4.5 or less molar equivalents. The upper and lower limits of the amount of the sulfur-containing inorganic compound can be arbitrarily combined, and the molar amount of sulfur atoms in the sulfur-containing inorganic compound relative to 12 molar amounts of molybdenum atoms in the source compound is preferably 0.1 to 4.9 molar amounts, more preferably 0.2 to 4.8 molar amounts, even more preferably 0.3 to 4.7 molar amounts, even more preferably 0.3 to 4.6 molar amounts, and even more preferably 0.4 to 4.5 molar amounts. In the present invention, only one type of sulfur-containing inorganic compound may be used, or two or more types may be used. When two or more types are used, it is preferable that the total amount is within the above range.

[0025] [Aqueous liquid] The starting materials used are aqueous liquids, which serve to dissolve and / or disperse the catalyst component element supply compounds, the sulfur-containing inorganic compound, and other components that are added as needed. Examples of aqueous liquids include water, an aqueous alcohol solution, an aqueous organic acid solution, an aqueous aldehyde solution, and an aqueous ketone solution, with water being preferred. The amount of the aqueous liquid is preferably 200 parts by mass or more and 2000 parts by mass or less per 100 parts by mass of the total of the catalyst component element supply source compounds and the sulfur-containing inorganic compound.

[0026] (2) Liquid preparation process (2) The liquid preparation step is a step of dissolving and / or dispersing a supply source compound of multiple catalyst component elements including molybdenum and a sulfur-containing inorganic compound in an aqueous liquid to obtain a starting material mixture. The liquid preparation step allows the starting materials to be uniformly dissolved or dispersed. In the present invention, it is preferable that the starting materials are dissolved in an aqueous liquid.

[0027] In the present invention, the supply source compound and the sulfur-containing inorganic compound are dissolved and / or dispersed in the aqueous liquid, and the supply source compound and the sulfur-containing inorganic compound may be added to the aqueous liquid simultaneously, or either one may be added first. In the present invention, it is preferable to add at least a part of the source compound to the aqueous liquid and then add the sulfur-containing inorganic compound, which makes it easier for the sulfur-containing inorganic compound to mix with the source compound, thereby making it possible to obtain a catalyst with a higher conversion rate and higher selectivity even at a low reaction temperature. The temperature of the prepared solution is usually 40°C or higher and 100°C or lower.

[0028] The pH of the starting material mixture obtained in the liquid preparation step is not particularly limited, but is preferably 5.5 or higher, more preferably 5.6 or higher, and is preferably 6.7 or lower, more preferably 6.5 or lower. By adjusting the pH to be equal to or higher than the above lower limit or equal to or lower than the above upper limit, it is possible to obtain a catalyst with a higher conversion rate and higher selectivity even at a low reaction temperature. The upper and lower limits of the pH of the starting material mixture can be arbitrarily combined, and are preferably 5.5 or more and 6.7 or less, more preferably 5.5 or more and 6.5 or less, and even more preferably 5.6 or more and 6.5 or less.

[0029] (3) Powderization process (first powderization process) The catalyst production method of the present invention includes a first powdering step of drying the starting material mixture to obtain a first powder. By drying the starting material mixture, the aqueous liquid can be removed from the starting material mixture. The drying can be carried out by a known method, for example, drum drying, freeze drying, spray drying, etc., and spray drying is preferred. The temperature during the drying is not particularly limited, but is preferably 80° C. or higher, more preferably 100° C. or higher, and even more preferably 110° C. or higher, and is preferably 200° C. or lower, more preferably 180° C. or lower, and even more preferably 160° C. or lower. By setting the temperature within the above range, the first powder can be obtained more efficiently. The upper and lower limits of the drying temperature can be arbitrarily combined, and are preferably 80°C or higher and 200°C or lower, more preferably 100°C or higher and 180°C or lower, and even more preferably 115°C or higher and 160°C or lower. At this time, it is preferable to dry the first powder so that the average particle size (D50) of the obtained first powder becomes 20 to 60 μm.

[0030] In the present invention, the difference between the ignition loss of the first powder at 250°C and the ignition loss of the first powder at 500°C (hereinafter referred to as "the ignition loss difference Y 1") is preferably in the range of 16% to 27%. By adopting such a configuration, the sulfur-containing inorganic compound is less likely to decompose until the drying step (4), and the decomposition progresses significantly in the drying step (4). Furthermore, since the sulfur-containing inorganic compound requires oxygen during decomposition, it is presumed that oxygen is extracted from the source compound of the catalyst component element, thereby effectively promoting the reduction of the source compound of the catalyst component element. First powder burn loss difference Y 1 is determined by the difference between the ignition loss of the first powder at 500°C and the ignition loss of the first powder at 250°C. The loss on ignition refers to the ratio of the mass of the first powder reduced after heating to the mass of the first powder before heating. The same measurement is also performed for the second powder. Burning loss (%)X=[(W 0 -W 1 ) / W 0 ] x 100 (W 0 : mass of powder before heating (g), W 1 : mass of powder after heating (g) First powder burn loss difference Y 1 =X 500 -X 250 (X 500 : Ignition loss at 500℃, X 250 : Ignition loss at 250℃)

[0031] The ignition loss difference Y of the first powder 1 is more preferably 25% or less, further preferably 23% or less, and is preferably 18% or more, more preferably 20% or more. By making the ratio equal to or greater than the lower limit, it is possible to produce an unsaturated carboxylic acid with a higher conversion rate and higher selectivity even at a low reaction temperature. The ignition loss difference Y of the first powder 1 The upper and lower limits can be arbitrarily combined, and are preferably 18% or more and 25% or less, and more preferably 20% or more and 23% or less. In the present invention, only one sulfur-containing inorganic compound may be used, or a mixture of two or more sulfur-containing inorganic compounds may be used. When a mixture of two or more sulfur-containing inorganic compounds is used, it is preferable that the content of the mixture is within the above range.

[0032] Here, Burning Weight Loss Y 1 The first powder to be measured means the powder immediately after drying in the first powdering step (3) in which the starting material mixture is dried to obtain the first powder.

[0033] (4) Drying process (4) The drying step is a step in which the first powder is heated to obtain a dried product. The heat treatment in the drying step crystallizes the catalyst components to make them easier to mold. Furthermore, it is presumed that the sulfur-containing inorganic compounds decompose, and the sulfur components reduce the source compounds (oxygen remaining in the catalyst components). The drying temperature in the drying step is preferably 330° C. or higher, more preferably 350° C. or higher, even more preferably 370° C. or higher, and more preferably 380° C. or higher, and is preferably 450° C. or lower, more preferably 430° C. or lower, and even more preferably 420° C. or lower. By setting the temperature to be equal to or higher than the lower limit and equal to or lower than the upper limit, it is possible to obtain a catalyst with a higher conversion rate and higher selectivity even at a low reaction temperature. The upper and lower limits of the drying temperature can be arbitrarily combined, and are preferably 330°C or higher and 450°C or lower, more preferably 350°C or higher and 450°C or lower, even more preferably 370°C or higher and 430°C or lower, and even more preferably 380°C or higher and 420°C or lower.

[0034] The heat treatment in the drying step is preferably carried out in an atmosphere with a low oxygen concentration, which is presumed to facilitate the reduction reaction of the supply source compound (oxygen remaining in the catalyst component). The oxygen concentration during the heat treatment is preferably 10% or less, more preferably 1% or less, and further preferably is carried out in an inert gas atmosphere. The heating time for the heat treatment is preferably 10 minutes or more and 10 hours or less.

[0035] (5) Powderization process (second powderization process) (5) The powdering step (second powdering step) is a step of obtaining a second powder from the dried product. In the present invention, the dried product may be used as the second powder as it is, or the second powder may be obtained from the dried product.

[0036] In the present invention, the difference between the ignition loss of the second powder at 250°C and the ignition loss of the second powder at 500°C (hereinafter referred to as "the ignition loss difference Y 2 ") is preferably in the range of 0.1% to 8%. The ignition loss difference Y of the second powder 2 is more preferably 7.0% or less, even more preferably 6.5% or less, and preferably 6.0% or less, and is preferably 0.2% or more, more preferably 0.3% or more, and even more preferably 0.5% or more. By making the content equal to or greater than the lower limit, even if the reaction temperature is low, an unsaturated carboxylic acid can be produced with a higher conversion rate and higher selectivity. The ignition loss difference Y of the second powder 2 The upper and lower limits can be arbitrarily combined, and are preferably 0.2% or more and 7.0% or less, more preferably 0.3% or more and 6.5% or less, and even more preferably 0.5% or more and 6.0% or less.

[0037] Here, Burning Weight Loss Y 2 The second powder to be measured means the powder immediately after drying (4) above.

[0038] By carrying out the second powdering step, it is possible to prevent unevenness during molding and to adjust the particle size of the powder. Specifically, the particle size of the powder is preferably adjusted to 500 μm or less, more preferably 300 μm or less. The particle size here is the particle size set by the pulverizer. The lower limit of the particle size of the powder is preferably 10 μm or more as the D50 value.

[0039] (6) Molding process (6) The molding step is a step of supporting the second powder on a granular carrier and / or molding it into a ring shape to obtain a catalyst precursor. The second powder is the dried product and / or a second powder obtained from the dried product. In the molding process, the second powder can be supported on the carrier to form a catalyst in the shape of a sphere or the like. The carrier is an inert component and is preferably made of silicon carbide, alumina, mullite, alundum, silica, etc. In the present invention, an alumina-silica carrier is an example. The carrier is in the form of granules, and is usually approximately spherical. The particle size (diameter) of the carrier is preferably 2.5 mm or more and 10 mm or less. If the granule-like carrier is not spherical, the particle size of the carrier is the particle size of a sphere having the same volume as the granule-like carrier. The particle size here is D50. The carrier preferably has a porosity of 30 to 50% and a water absorption rate of 10 to 30%. Alternatively, the second powder can be molded into a ring shape, which is preferably a hollow cylinder.

[0040] The molding may or may not involve the use of a binder, and examples of the binder include polyols such as glycerin. In the present invention, the binder may be substantially water. The binder being substantially water means that the binder is more than 90% by mass water, preferably more than 95% by mass water, more preferably more than 97% by mass water, and even more preferably more than 99% by mass water. In the present invention, even if the binder is substantially water, a good catalyst can be molded.

[0041] In addition, a molding aid or a strength improving material may be used in the molding step. Examples of molding aids include silica gel, diatomaceous earth, alumina powder, etc. The amount of molding aid used is usually 5 to 60 parts by mass per 100 parts by mass of the total mass of the second powder and the carrier. Examples of the strength improving agent include inorganic fibers such as ceramic fibers, whiskers, etc. The amount of the strength improving agent used is usually 1 to 30 parts by mass per 100 parts by mass of the total mass of the second powder and the carrier. The molding can be carried out by a rolling granulation method, etc. For details of the rolling granulation method, refer to the description in Japanese Patent No. 3786297.

[0042] (7) Firing process The (7) calcination step is a step in which the second powder is supported on a granular support and / or molded into a ring shape, and the catalyst precursor is baked to solidify the crystallized state. The calcination step may be performed before the (6) molding step, after the (6) molding step, or before or after the (6) molding step. Furthermore, if the catalyst component derived from the supply source compound is already sufficiently crystallized, the calcination step may not be performed. In the present invention, it is preferable to carry out the (7) firing step after the (6) molding step. The heating temperature in the calcination step is preferably 330° C. or higher, more preferably 350° C. or higher, and even more preferably 370° C. or higher, and is preferably 450° C. or lower, and more preferably 420° C. or lower. By setting the temperature to be equal to or higher than the above lower limit and equal to or lower than the above upper limit, it is possible to obtain a catalyst with a higher conversion rate and higher selectivity even at a low reaction temperature. The upper and lower limits of the heating temperature in the firing step can be arbitrarily combined, and are preferably 330°C or higher and 450°C or lower, more preferably 350°C or higher and 450°C or lower, and even more preferably 370°C or higher and 420°C or lower.

[0043] The heat treatment in the firing step can be carried out in an air atmosphere. The heat treatment time in the baking step is preferably 10 minutes or more and 10 hours or less.

[0044] (8) Catalyst for synthesizing unsaturated carboxylic acids The catalyst for synthesizing an unsaturated carboxylic acid of the present invention can be obtained by the method for producing a catalyst for synthesizing an unsaturated carboxylic acid of the present invention. The catalyst for synthesizing an unsaturated carboxylic acid is preferably used as a catalyst when synthesizing an unsaturated carboxylic acid from an unsaturated aldehyde. As the unsaturated aldehyde, acrolein and methacrolein are preferred, and acrolein is more preferred. As the unsaturated carboxylic acid, acrylic acid and methacrylic acid are preferred, and acrylic acid is more preferred. Acrolein is synthesized from propylene, and methacrolein is synthesized from isobutene. A catalyst may also be used for synthesizing unsaturated aldehydes, and a Mo-Bi catalyst is preferably used. The catalyst for synthesizing unsaturated aldehydes is preferably spherical or ring-shaped. [Example]

[0045] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

[0046] Example 1 [Liquid preparation process] 1800 mL of warm water was placed in a container, and 30 g of ammonium paratungstate was added and dissolved. Next, 64 g of ammonium metavanadate was added and dissolved. Next, 486 g of ammonium molybdate was further added and dissolved. Next, 91 g of ammonium sulfate was further added and dissolved to obtain a solution (hereinafter referred to as "Solution A") The amount of ammonium sulfate added was 0.4 moles in terms of sulfur atoms relative to 12 moles in terms of molybdenum atoms in the source compound. Next, a solution prepared by dissolving 69 g of copper sulfate in 100 mL of warm water was added to the solution A and mixed to make a homogeneous mixture. Next, 13 g of antimony trioxide was added to this mixed liquid and stirred to obtain a mixed liquid of starting materials. The pH of the resulting adjusted solution was between 5.5 and 6.5.

[0047] [First powderization process, drying process, second powderization process] The resulting starting material mixture was spray-dried at 150° C. The mass (g) of the resulting powder (first powder) before heating, the mass (g) after heating to 250° C., and the mass (g) after heating to 500° C. were measured, and the ignition losses (%) at 250° C. and 500° C. were calculated. Burning loss (%)X=[(W 0 -W 1 ) / W 0 ] x 100 (W 0 : mass of powder before heating (g), W 1 : mass of powder after heating (g) First powder burn loss difference Y 1 were measured and are shown in Table 1. Burning weight loss difference Y 1 =X 500 -X 250 (X 500 : Ignition loss at 500℃, X 250 : Ignition loss at 250℃)

[0048] Next, the first powder was heat-treated for 1 hour in an inert gas atmosphere (oxygen concentration 0%) at a drying temperature (370°C) shown in Table 1 to obtain a dried product.

[0049] The obtained dried product was pulverized to 200 μm or less using a stirring blade pulverizer, and this pulverized product was used as a supporting powder (second powder). The mass (g) of the obtained second powder before heating, the mass (g) after heating to 250°C, and the mass (g) after heating to 500°C were measured, and the ignition loss (%) at 250°C and 500°C was calculated. Burning loss (%)X=[(W 0 -W 1 ) / W 0 ] x 100 (W 0 : mass of powder before heating (g), W 1 : mass of powder after heating (g) Second powder burn loss difference Y 2 was calculated and shown in Table 1. Second powder burn loss difference Y 2 =X 500 -X 250 (X 500 : Ignition loss at 500℃, X 250 : Ignition loss at 250℃)

[0050] Furthermore, the scorching loss difference Y 1 and Y 2 From this, the ignition loss difference Z was calculated. Burning weight loss difference ratio Z = (Y 2 / Y 1 ) x 100 (Y 1 : Ignition loss difference of the first powder, Y 2 : Second powder burn loss difference)

[0051] [Molding process, firing process] 100 g of a 4.5 mm diameter spherical inert carrier composed mainly of alumina-silica was introduced into a tumbling granulator, and then 16.7 mass % of the total binder amount of 18.0 g, Binder A, was introduced into the tumbling granulator. The binder was pure water. Further, 70.0 g of the supporting powder and 83.3 mass % of the binder B out of a total binder amount of 18.0 g were alternately introduced into the tumbling granulator to support the powder, thereby obtaining a molded catalyst precursor. This catalyst precursor was calcined in an air atmosphere at 390°C for 3 hours to obtain a catalyst. The composition ratio of the catalyst component elements (excluding oxygen) of this catalyst was as follows: Mo 12 V 2.4 W 0.5 Cu 0.9 Sb 0.4

[0052] [Synthesis of acrylic acid] A cylindrical reaction tube with an inner diameter of 21 mm was packed with 33 mL of the catalyst. The reaction tube was heated, and a raw material gas (acrolein 6 vol.%, steam 22 vol.%, oxygen 8 vol.%, nitrogen 64 vol.%) was introduced from the inlet of the reaction tube. A gas-phase catalytic oxidation reaction of acrolein was carried out at an SV (space velocity; flow rate of raw material gas per unit time / apparent volume of packed catalyst) of 1550 / hr. The reaction temperature was adjusted so that the conversion of acrolein was 99.0 mol%. The reaction evaluation results are shown in Table 1. The acrolein conversion, the acrylic acid selectivity, and the acrylic acid yield are defined by the following formulas (1) to (3). (1) Acrolein conversion rate (mol%) = 100 × (number of moles of acrolein reacted) / (number of moles of acrolein supplied) (2) Acrylic acid selectivity (mol%) = 100 × (moles of acrylic acid produced) / (moles of acrolein converted) (3) Acrylic acid yield (mol %) = 100 × (moles of acrylic acid produced) / (moles of acrolein supplied)

[0053] [Example 2, Example 3, Example 4, Comparative Example 1, Comparative Example 2] The drying temperature was changed to 390°C, 410°C, 430°C, 350°C, and 450°C in the order of Example 2, Example 3, Example 4, Comparative Example 1, and Comparative Example 2 to adjust the difference in ignition loss between each Example and Comparative Example, but the rest was performed in the same manner. The composition ratios (excluding oxygen) of the obtained catalysts in all cases were as follows. Mo 12 V 2.4 W 0.5 Cu 0.9 Sb 0.4

[0054] [Table 1]

[0055] In Table 1, Y 1 is the ignition loss difference of the first powder (unit: %), Y 2 indicates the ignition loss difference of the second powder (unit: %). Z is the ignition loss difference ratio Z = (Y 2 / Y 1 ) × 100. The units of the acrylic acid selectivity and the acrylic acid yield are mol %. As is clear from the above results, the catalyst obtained by the production method of the present invention was able to sufficiently convert unsaturated aldehydes and increase the selectivity and yield of the obtained unsaturated carboxylic acid even under conditions of low reaction temperature. In contrast, the catalyst obtained by the comparative production method required a high reaction temperature in order to sufficiently convert the unsaturated aldehyde.

[0056] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.

Claims

1. a liquid preparation step of dissolving and / or dispersing a supply source compound of a plurality of catalyst component elements including molybdenum and a sulfur-containing inorganic compound in an aqueous liquid to obtain a starting material mixture; a first powdering step of drying the starting material mixture to obtain a first powder; A drying step of obtaining a dried product by heat-treating the first powder; and A molding step of forming the dried product into a second powder and / or obtaining a second powder from the dried product, supporting the second powder on a granular carrier, and / or molding the second powder into a ring shape to form a catalyst precursor. A method for producing a catalyst for synthesizing an unsaturated carboxylic acid, comprising: A method for producing a catalyst for synthesizing unsaturated carboxylic acids, wherein the ratio of the difference between the ignition loss of the second powder at 500°C and the ignition loss of the second powder at 250°C to the difference between the ignition loss of the first powder at 500°C and the ignition loss of the first powder at 250°C is in the range of 0.4% or more and 45% or less. Ignition loss (%) X = [(W ０ -W １ ) / W ０ ]×100 (W ０ : mass of powder before heating (g), W １ : mass of powder after heating (g) Ignition loss difference Y (%) = X ５００ -X ２５０ (X ５００ : Ignition loss at 500 ° C, X ２５０ : Ignition loss at 250 ° C) Burning weight loss ratio Z = (Y ２ / Y １ ) x 100 (Y １ : Ignition loss difference of the first powder, Y ２ : The difference in the burning loss of the second powder)

2. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, wherein the sulfur-containing inorganic compound does not contain copper sulfate.

3. 3. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, wherein the sulfur-containing inorganic compound is added after at least a portion of the source compound is added to the aqueous liquid.

4. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1 or 2, wherein the sulfur-containing inorganic compound comprises a sulfate.

5. 3. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, wherein the catalyst for synthesizing an unsaturated carboxylic acid has a composition represented by formula (1): *] １２ . ａ ︸ ｂ u ｃ ﹹ ｄ 3) ｅ : ｆ 3) ｇ 4 ｈ . ｉ () (In formula (1), X represents Nb and / or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and Z represents at least one element selected from the group consisting of Fe, Co, Ni, and Bi. a to i represent atomic ratios of each element and are in the ranges of 0<a≦12, 0≦b≦12, 0<c≦12, 0≦d≦8, 0≦e≦500, 0≦f≦500, 0≦g≦500, and 0≦h≦500, and i is a value that satisfies the oxidation state of the other elements.)

6. 3. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, wherein the heat treatment in the drying step is carried out in an atmosphere having an oxygen concentration of 10% or less.

7. 3. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, wherein the heat treatment temperature is 330°C or higher and 450°C or lower.

8. the sulfur-containing inorganic compound does not include copper sulfate and includes a sulfate; adding at least a portion of the source compound to the aqueous liquid, followed by adding the sulfur-containing inorganic compound; The composition formula of the catalyst component elements of the catalyst for synthesizing an unsaturated carboxylic acid is represented by formula (1), The heat treatment in the drying step is carried out in an atmosphere having an oxygen concentration of 10% or less, 2. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, wherein the heat treatment temperature is 330°C or higher and 450°C or lower. *] １２ . ａ ︸ ｂ u ｃ ﹹ ｄ 3) ｅ : ｆ 3) ｇ 4 ｈ . ｉ () (In formula (1), X represents Nb and / or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and Z represents at least one element selected from the group consisting of Fe, Co, Ni, and Bi. a to i represent atomic ratios of each element and are in the ranges of 0<a≦12, 0≦b≦12, 0<c≦12, 0≦d≦8, 0≦e≦500, 0≦f≦500, 0≦g≦500, and 0≦h≦500, and i is a value that satisfies the oxidation state of the other elements.)

9. 9. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, 2 or 8, wherein the catalyst for synthesizing an unsaturated carboxylic acid is a catalyst for synthesizing acrylic acid.

10. A catalyst for synthesizing an unsaturated carboxylic acid, obtained by the method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, 2 or 8.

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