catalyst

Abstract

To provide a catalyst used when contacting and oxidizing olefin and oxygen containing gas in a vapor phase to manufacture unsaturated aldehyde and unsaturated carboxylic acid, excellent in conversion ratio, high in selectivities of unsaturated aldehyde and unsaturated carboxylic acid, capable of improving a yield and excellent in strength.SOLUTION: The catalyst for manufacturing unsaturated aldehyde and unsaturated carboxylic acid includes pores having a pore diameter of 1 μm or more and an integration pore volume (A) of 100 μm or less 0.12 ml / g and 0.19 ml / g or less. In a pulverized material obtained by pulverizing the catalyst on specific conditions, a ratio (A / B) of the integration pore volume (A) to an integration pore volume (B) of pores having 1 μm or more and 100 μm or less of a pore diameter of the pulverized material without passing through a Tyler six mesh is 0.30 or more and 0.87 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids. [Background technology]

[0002] A catalyst containing molybdenum as an essential component is generally used as a catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids by vapor-phase catalytic oxidation of olefins having 3 or 4 carbon atoms, etc., with an oxygen-containing gas. Specifically, improvements have been vigorously pursued from various perspectives in the catalysts used in producing acrolein and acrylic acid from propylene and the like, and in producing methacrolein and methacrylic acid from isobutylene and the like.

[0003] The process for producing unsaturated aldehydes or unsaturated carboxylic acids comprises subjecting an olefin and an oxygen-containing gas to gas-phase catalytic oxidation in a fixed-bed reactor packed with a catalyst.

[0004] The catalyst packed in the fixed-bed reactor has a shape such as a cylinder, ring, tablet, or sphere, and generally, a catalyst obtained by molding a powder of a catalytically active component or a catalyst obtained by supporting a catalytically active component on an inert carrier having a shape similar to the above-mentioned shapes is used.

[0005] Patent Document 1 discloses a catalyst for propylene oxidation that contains molybdenum, iron, and bismuth and has a specific specific surface area and a specific pore volume. Patent Document 2 discloses a catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids, in which the pore volume present in a specific pore diameter is within a specific range. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 63-200839 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-176931 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the catalyst described in Patent Document 1 is used to perform gas-phase catalytic oxidation of olefins such as propylene with an oxygen-containing gas, the reaction efficiency is insufficient, and the corresponding unsaturated aldehydes such as acrolein and unsaturated carboxylic acids such as acrylic acid cannot be obtained in high yields. Furthermore, when gas-phase catalytic oxidation is performed at high temperatures to improve catalyst activity, side reactions occur, further reducing the yield. Furthermore, the strength of the catalyst is insufficient, resulting in powdering and cracking of the catalyst, making it impossible to perform stable and efficient gas-phase catalytic oxidation reactions over long periods of time. Furthermore, the catalyst described in Patent Document 2 also has room for improvement in the yield of unsaturated carboxylic acid and the strength of the catalyst.

[0008] The present invention has been made to solve the above-mentioned problems. Specifically, it is an object of the present invention to provide a catalyst for use in the gas-phase catalytic oxidation of an olefin such as propylene with an oxygen-containing gas to produce the corresponding unsaturated aldehyde such as acrolein and unsaturated carboxylic acid such as acrylic acid, which has excellent raw material conversion and can selectively produce the desired unsaturated aldehyde and unsaturated carboxylic acid in high yield even under conditions in which the feed rate of the raw material, olefin such as propylene, is large, i.e., the load on the catalyst is high, and which has high strength and is capable of performing the gas-phase catalytic oxidation reaction stably for a long period of time. [Means for solving the problem]

[0009] As a result of intensive research by the present inventors to solve the above problems, it has been found that a catalyst in which the cumulative pore volume (A) of pores having a pore volume of 1 μm or more and 100 μm or less is 0.12 ml / g or more and 0.19 ml / g or less, and in which a pulverized product obtained by pulverizing the catalyst under specific conditions, which does not pass through a Tyler 6 mesh, has a cumulative pore volume (A) of pores having a pore diameter of 1 μm or more and 100 μm or less (B), has a ratio (A / B) of 0.30 or more and 0.87 or less, can be obtained. The inventors have found that when this catalyst is used for gas-phase catalytic oxidation of olefins with an oxygen-containing gas, even under conditions where the olefin supply amount is large and the load on the catalyst is high, the olefin conversion rate is excellent, and the selectivity for unsaturated aldehydes such as acrolein and unsaturated carboxylic acids such as acrylic acid is good, with the selectivity for unsaturated carboxylic acids such as acrylic acid being particularly high, making it possible to improve the yields of unsaturated aldehydes such as acrolein and unsaturated carboxylic acids such as acrylic acid. This has led to the present invention.

[0010] That is, the present invention is as follows. [1] A catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids, The catalyst has a cumulative pore volume (A) of pores having a pore diameter of 1 μm or more and 100 μm or less of 0.12 ml / g or more and 0.19 ml / g or less, and A catalyst in which, among the pulverized product obtained by pulverizing the catalyst under pulverization condition A, the pulverized product that does not pass through a Tyler 6 mesh has an integrated pore volume (A) of pores having a pore diameter of 1 μm or more and 100 μm or less to an integrated pore volume (B) of the pores, the ratio (A / B) of the integrated pore volume (A) to the integrated pore volume (B) of 0.30 or more and 0.87 or less (Pulverization condition A). A tumbling granulator has a cylinder fixed vertically, a disk installed horizontally at the bottom end of the cylinder, and the disk rotates around the center of the cylinder, causing the particles to rotate and revolve. 100 g of catalyst is placed into the tumbling granulator, and the disk begins operating at a relative centrifugal acceleration of 12 G, which is increased to 130 G within 1 minute, and the disk continues to rotate at the relative centrifugal acceleration of 130 G for 2 minutes. The relative centrifugal acceleration is a numerical value that expresses the magnitude of the centrifugal force applied per unit weight of the catalyst as a ratio to the acceleration of gravity, and is expressed by the following formula (X). F=1118×r×N 2 x10 -8 Formula (X) F: relative centrifugal acceleration (G), r: Distance from the center of rotation to the bottom of the cylinder (cm) N: rotation speed (rpm)

[0011] [2] The catalyst according to [1], wherein the catalyst contains molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), and iron (Fe), and the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), and iron (Fe) in the catalyst satisfies the following formula (1): Mo a Bi b Co c Ni d Fe e (1) (In the formula, a to e represent the atomic ratios of the respective elements, and when a=12, b=0.5 to 7, c=0.1 to 10, d=0.1 to 10, and e=0.05 to 5.)

[0012] [3] The catalyst according to [1] or [2], wherein the catalyst comprises a support. [4] The catalyst according to any one of [1] to [3], wherein the catalyst has a spherical shape. [5] A method for producing acrolein and acrylic acid, comprising a step of gas-phase catalytic oxidation of propylene and an oxygen-containing gas using the catalyst according to any one of [1] to [4]. [Effects of the Invention]

[0013] According to the present invention, there is provided a catalyst which has high catalytic performance, is excellent in olefin conversion even under conditions of high catalyst load, and is capable of suppressing excessive oxidation reactions and producing unsaturated aldehydes such as acrolein and unsaturated carboxylic acids such as acrylic acid with high selectivity. Furthermore, the catalyst according to the present invention has high strength and is less prone to powdering. As a result, the catalyst can be efficiently packed into a reactor, and by using the catalyst, unsaturated aldehydes such as acrolein and unsaturated carboxylic acids such as acrylic acid, in particular unsaturated carboxylic acids such as acrylic acid, can be produced with high selectivity over a long period of time, starting from the beginning of the gas-phase catalytic oxidation. DETAILED DESCRIPTION OF THE INVENTION

[0014] The best mode for carrying out the present invention will be described in detail below, but the explanation of the constituent elements described below is a representative example of an embodiment of the present invention, and the present invention is not limited to these contents.

[0015] [catalyst] One embodiment of the present invention relates to a catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids, wherein the catalyst has an integrated pore volume (A) of pores having a pore diameter of 1 μm to 100 μm of 0.12 ml / g to 0.19 ml / g, and the ratio (A / B) of the integrated pore volume (A) of pores having a pore diameter of 1 μm to 100 μm in a pulverized product obtained by pulverizing the catalyst under pulverization condition A to the integrated pore volume (B) of pores having a pore diameter of 1 μm to 100 μm in a pulverized product that does not pass through a Tyler 6 mesh is 0.30 to 0.87. The ratio (A / B) is preferably 0.50 to 0.87, more preferably 0.65 to 0.87, and even more preferably 0.60 to 0.87. When the ratio (A / B) is within the above range, the catalyst has an excellent raw material conversion rate (hereinafter, sometimes simply referred to as "conversion rate") in the gas-phase catalytic oxidation of olefins, and is capable of producing unsaturated aldehydes and unsaturated carboxylic acids with high selectivity. In addition, the catalyst has high strength and tends to be less prone to powdering.

[0016] The ratio (A / B) will be explained in more detail below. The cumulative pore volume (A) reflects the volume of pores near the catalyst surface, while the cumulative pore volume (B) reflects the volume of pores inside the catalyst. In other words, a smaller cumulative pore volume (A) means a higher density of the catalyst surface, which increases the catalyst strength, but makes it difficult for the raw material gas to reach the catalyst interior, making it difficult for the catalytically active components present inside the catalyst to contribute to the catalytic reaction, resulting in a decrease in conversion. On the other hand, a larger cumulative pore volume (A) means a lower density of the catalyst surface, which decreases the catalyst strength, but makes it easier for the raw material gas to reach the catalyst interior, and effectively utilizes the catalytically active components present not only near the catalyst surface but also inside the catalyst, improving the conversion. When the ratio (A / B) is within the above range, the balance between the raw material conversion rate and the catalyst strength is optimized.

[0017] The catalyst crushing condition A refers to a crushing process carried out by placing 100 g of catalyst into a tumbling granulator in which a cylinder is fixed vertically, a disk is installed horizontally at the bottom end of the cylinder, and the disk rotates around the center of the cylinder, causing the particles to rotate and revolve around their own axis, and starting the operation of the disk at a relative centrifugal acceleration of 12 G, increasing the relative centrifugal acceleration to 130 G within one minute, and continuing the rotation of the disk at the relative centrifugal acceleration of 130 G for two minutes. The relative centrifugal acceleration is a numerical value that expresses the magnitude of the centrifugal force applied per unit weight of the catalyst as a ratio to the acceleration of gravity, and is expressed by the following formula (X). F=1118×r×N 2 x10 -8 Formula (X) F: relative centrifugal acceleration (G), r: Distance from the center of rotation to the bottom of the cylinder (cm) N: rotation speed (rpm)

[0018] Specifically, the catalyst is crushed under crushing condition A by, for example, placing 100 g of the catalyst into a Marumerizer QJ-230T-2 model (cylinder diameter 23 cm) manufactured by Dalton Co., Ltd., starting operation at a rotation speed of 300 rpm, increasing the rotation speed to 1000 rpm within 1 minute, and continuing operation at a rotation speed of 1000 rpm for 2 minutes.

[0019] The cumulative pore volume can be measured by mercury intrusion porosimetry, which involves subjecting a sample to reduced pressure (50 μmHg or less) for 10 minutes, and then measuring the total pore volume (cumulative pore volume) from the mercury intrusion / extrusion curve using an Autopore IV 9520 manufactured by Micromeritics Japan. Furthermore, the conversion rate of the raw material (olefin), the selectivity of the unsaturated aldehyde, and the selectivity of the unsaturated carboxylic acid are calculated by the following formulas. Olefin conversion (mol%) = (moles of reacted olefin / moles of supplied olefin) x 100 Selectivity of unsaturated aldehyde (mol%) = (moles of unsaturated aldehyde produced / moles of olefin reacted) x 100 Selectivity of unsaturated carboxylic acid (mol%) = (number of moles of unsaturated carboxylic acid produced / number of moles of olefin reacted) × 100

[0020] The cumulative pore volume (A) of the pores having a pore diameter of 1 μm or more and 100 μm or less is 0.12 ml / g or more and 0.19 ml / g or less, preferably 0.12 ml / g or more and 0.18 ml / g or less, and more preferably 0.15 ml / g or more and 0.18 ml / g or less. When the cumulative pore volume (A) is equal to or less than the upper limit, damage and crushing of the catalyst are suppressed. Furthermore, when the cumulative pore volume (A) is equal to or more than the lower limit, it is easy to achieve a high raw material conversion rate, unsaturated aldehyde selectivity, unsaturated carboxylic acid selectivity, and unsaturated carboxylic acid selectivity ratio. The selectivity ratio of the unsaturated carboxylic acid refers to the ratio of the selectivity of the unsaturated carboxylic acid to the sum of the selectivity of the unsaturated aldehyde and the selectivity of the unsaturated carboxylic acid.

[0021] The catalyst contains molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), and iron (Fe), and it is preferable that the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), and iron (Fe) in the catalyst satisfies the following formula (1): Mo a Bi b Co c Ni d Fe e (1) (In the formula, a to e represent the atomic ratios of the respective elements, and when a=12, b=0.5 to 7, c=0.1 to 10, d=0.1 to 10, and e=0.05 to 5.) By satisfying the above formula (1), it becomes possible to obtain an excellent conversion rate of propylene and to produce unsaturated aldehydes such as acrolein and unsaturated carboxylic acids such as acrylic acid with high selectivity.

[0022] Furthermore, the catalyst preferably contains a carrier. It is more preferable that the carrier is inert to the reaction of gas-phase catalytic oxidation of an olefin with an oxygen-containing gas. Examples of the carrier include silica, silicon carbide, alumina, mullite, alundum, etc., and alumina is more preferable. By containing a carrier, the catalytic function can be exerted not only on the surface but also inside of the catalyst, and an improvement in the selectivity of unsaturated aldehyde and the selectivity of unsaturated carboxylic acid can be expected.

[0023] The amount of the support is such that the ratio of the amount of the catalytically active component powder to the total amount of the catalytically active component powder and the amount of the support (amount of catalytically active component powder / (amount of catalytically active component powder + amount of support)) is usually 10% by weight to 90% by weight, preferably 30% by weight to 80% by weight. By setting the ratio within this range, the cumulative pore volume (A) of the produced catalyst is likely to fall within the range of the present invention.

[0024] In addition, the shape of the catalyst may be ring-shaped, cylindrical, tablet-shaped, spherical, etc., but spherical is preferred. The spherical shape does not only mean a geometrically perfect sphere, but also an ellipsoid. However, a shape close to a perfect sphere is more preferable. In this embodiment, a catalyst having a spherical shape is defined as a catalyst having a ratio of the longest diameter (major axis diameter) to the shortest diameter (minor axis diameter) of three mutually perpendicular diameters of the catalyst particle of 2 or less, preferably 1.3 or less. By using a spherical catalyst, there is a possibility that an increase in pressure loss in the catalyst packed bed in a fixed bed reactor can be suppressed. The ratio of the major axis diameter to the minor axis diameter of the catalyst can be calculated by measuring the major axis diameter and minor axis diameter of each of 100 catalyst particles using a high-precision two-dimensional dimension measuring instrument VM-8040 manufactured by Keyence Corporation, then calculating the average major axis diameter and average minor axis diameter, and then calculating the ratio.

[0025] Furthermore, the catalyst powdering rate is preferably 3.0% or less, more preferably 1.0% or less. Within this range, the catalyst has excellent strength, and the catalyst can be packed into the reaction tube of a fixed-bed reactor without powdering or cracking. The catalyst powder rate can be calculated, for example, by inserting a funnel (conical upper opening diameter: 150 mm, conical lower opening diameter: 25 mm) into the top of an acrylic cylinder (φ66 mm) that is 1 m high, pouring about 20 g of catalyst (powder rate measurement sample) into the conical upper part of the funnel, allowing it to fall through the cylinder into a tray placed at the bottom of the cylinder, recovering the fallen powder rate measurement sample from the tray, and measuring the weight of the fine particles sieved through a sieve with 2.36 mm openings (powdered weight), using the following formula: Powdering rate (%) = (powdered weight / weight of sample for powdering rate measurement) x 100

[0026] Next, a preferred method for producing the catalyst will be described. The method for producing the catalyst preferably includes the following two steps. Step (a): A step of combining and heating source compounds of elements including molybdenum, bismuth, cobalt, nickel, and iron (hereinafter sometimes referred to as "catalytically active elements") in an aqueous system to obtain a powder of catalytically active components. Step (b): A step of molding the powder of the catalytically active component obtained in step (a) into a molded body.

[0027] In the above step (a), the integration of the respective supply source compounds of catalytically active elements including molybdenum, bismuth, cobalt, nickel, and iron in an aqueous system means that aqueous solutions or aqueous dispersions of the respective supply source compounds of the catalytically active elements are mixed together or stepwise, followed by aging treatment. Specifically, there are the following methods (a1) to (a5), all of which are included in the concept of the integration of the respective supply source compounds of the catalytically active elements in an aqueous system. (a1) A method in which the above-mentioned source compounds are mixed together; (a2) A method of mixing the above-mentioned source compounds together and subjecting them to aging treatment; (a3) A method of mixing the above-mentioned source compounds stepwise; (a4) A method of repeating a cycle of stepwise mixing and aging the above-mentioned source compounds; (a5) A method of combining the above-mentioned (a1) to (a4). Here, the term "aging" refers to "the process of treating industrial raw materials or semi-finished products under specific conditions such as a fixed time and a fixed temperature to obtain or increase required physical or chemical properties or to promote a predetermined reaction" (Chemical Dictionary / Kyoritsu Shuppan). In this invention, the fixed time refers to a range of 10 minutes to 24 hours, and the fixed temperature refers to a range from room temperature to the boiling point of the aqueous solution or aqueous dispersion.

[0028] The heating in step (a) refers to heat treatment for forming a composite metal oxide from the individual metal oxides of the catalytically active element source compounds, for forming a composite metal oxide from the composite compound resulting from the integration of the catalytically active element source compounds, and for forming a final composite metal oxide. The heating is not necessarily limited to a single step. That is, the heating can be performed at any time between and / or during the integration steps (a1) to (a5), and may be performed additionally after integration as needed. The heating temperature is typically in the range of 200°C to 600°C. Furthermore, in the above integration and heating, drying, pulverization, etc. may be performed as necessary. It may be carried out before, after or during this period.

[0029] Examples of molybdenum (Mo) source compounds include ammonium paramolybdate, molybdenum trioxide, molybdic acid, ammonium phosphomolybdate, and phosphomolybdic acid.

[0030] Examples of bismuth (Bi) source compounds include bismuth chloride, bismuth nitrate, bismuth oxide, and bismuth subcarbonate. The amount of the bismuth source compound charged is preferably such that, in the obtained catalyst, when a = 12, b = 0.5 to 7, more preferably b = 0.7 to 5.0, and even more preferably b = 1.0 to 4.9, in the above formula (1). When b is within the above range, a catalyst can be obtained that has a high conversion rate, a high selectivity for unsaturated aldehyde, a high selectivity for unsaturated carboxylic acid, and a high ratio of the selectivity for unsaturated carboxylic acid.

[0031] Examples of cobalt (Co) source compounds include cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt carbonate, and cobalt acetate. The amount of the cobalt source compound charged is preferably such that, in the obtained catalyst, when a = 12, c = 0.1 to 10, more preferably c = 0.3 to 5.0, and even more preferably c = 0.5 to 3.0, in the above formula (1). When c is within the above range, a catalyst can be obtained that has a high conversion rate, selectivity to unsaturated aldehyde, selectivity to unsaturated carboxylic acid, and a high ratio of selectivity to unsaturated carboxylic acid.

[0032] Examples of nickel (Ni) source compounds include nickel nitrate, nickel sulfate, nickel chloride, nickel carbonate, and nickel acetate. The amount of the nickel source compound charged is preferably such that, in the obtained catalyst, when a = 12 in the above formula (1), d = 0.1 to 10, more preferably d = 0.3 to 8, and even more preferably d = 0.5 to 5. When d is within the above range, a catalyst can be obtained that has a high conversion rate, a high selectivity for unsaturated aldehyde, a high selectivity for unsaturated carboxylic acid, and a high ratio of the selectivity for unsaturated carboxylic acid.

[0033] Examples of iron (Fe) source compounds include ferric nitrate, ferric sulfate, ferric chloride, and ferric acetate. The amount of the iron source compound charged is preferably such that, in the obtained catalyst, when a = 12 in the above formula (1), e = 0.05 to 5, more preferably e = 0.1 to 3, and even more preferably e = 0.2 to 2. When e is within the above range, the catalyst can have a high conversion rate, a high selectivity for unsaturated aldehyde, a high selectivity for unsaturated carboxylic acid, and a high ratio of the selectivity for unsaturated carboxylic acid.

[0034] The catalyst preferably further contains sodium (Na), potassium (K), and silicon (Si). That is, the catalyst preferably contains molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), iron (Fe), sodium (Na), potassium (K), and silicon (Si), and the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), iron (Fe), sodium (Na), potassium (K), and silicon (Si) in the catalyst preferably satisfies the following formula (2): Mo a Bi b Co c Ni d Fe e Na f K g Si h (2) (In the formula, a to h represent the atomic ratio of each element, and when a = 12, f = 0 to 2, g = 0 to 2, and h = 0 to 70; b to e are the same as b to e in formula (2), and preferred embodiments thereof are also the same.)

[0035] Sodium (Na) source compounds include sodium chloride, sodium carbonate, sodium nitrate, sodium sulfate, sodium acetate, sodium borate, etc. The amount of the sodium source compound charged is preferably an amount such that, in the obtained catalyst, when a = 12 in the above formula (2), f = 0 to 2, more preferably f = 0.1 to 1, and even more preferably f = 0.2 to 0.5. When f is equal to or greater than the above-mentioned lower limit, a catalyst having high selectivity to unsaturated aldehyde, high selectivity to unsaturated carboxylic acid, and high ratio of selectivity to unsaturated carboxylic acid can be obtained, and when f is equal to or less than the above-mentioned upper limit, a catalyst having excellent conversion can be obtained.

[0036] Examples of potassium (K) source compounds include potassium nitrate, potassium sulfate, potassium chloride, potassium carbonate, and potassium acetate. The amount of potassium source compound charged is preferably such that when a = 12, g = 0 to 2, more preferably g = 0.05 to 1, and even more preferably g = 0.05 to 0.5, of the resulting catalyst in the above formula (2). When g is equal to or greater than the above-mentioned lower limit, the catalyst can have high unsaturated aldehyde selectivity, unsaturated carboxylic acid selectivity, and unsaturated carboxylic acid selectivity ratio. When g is equal to or less than the above-mentioned upper limit, the catalyst can have an excellent conversion rate.

[0037] Examples of silicon (Si) source compounds include silica, granular silica, colloidal silica, and fumed silica. The amount of silicon source compound added is preferably such that, in the obtained catalyst, when a = 12 in the formula (2), h = 0 to 70, more preferably h = 5 to 50, and even more preferably h = 10 to 30. When h is equal to or greater than the lower limit mentioned above, the dispersibility of each component is improved, resulting in a catalyst with an excellent conversion rate. When h is equal to or less than the upper limit mentioned above, a balance between the silicon content and the content of other metals is maintained, resulting in a catalyst with an excellent conversion rate.

[0038] The above-mentioned step (b) is a step of molding the powder of catalytically active component obtained in step (a) into a molded body. The powder of catalytically active component obtained in step (a) has catalytic activity as it is, but since catalysts are generally loaded into a fixed-bed reactor and used in gas-phase catalytic oxidation, it is preferable to mold it. This is because molding the catalyst improves the workability when loading and unloading from the reactor and can suppress an increase in pressure loss during gas-phase catalytic oxidation. When the molded catalyst is spherical, the average diameter of the catalyst is preferably 2 mm to 15 mm, more preferably 3 mm to 10 mm. The average diameter of the catalyst can be determined by measuring the average diameter of each of 100 catalyst particles using a high-precision two-dimensional size measuring instrument VM-8040 manufactured by Keyence Corporation, and calculating the average value.

[0039] The method for molding the powder of the catalytically active component may be any conventionally known method, but there are, for example, the following two methods. One is a method in which, while the support is fluidized, the powder of the catalytically active component is supplied to the fluidized support, the powder of the catalytically active component is supported on the surface of the support, and the powder is granulated and molded into a molded body (hereinafter sometimes referred to as the "tumbling granulation method"). The other is a method in which the powder of the catalytically active component is placed in a mold and mechanically pressured to granulate and mold into a molded body (hereinafter sometimes referred to as the "tablet molding method").

[0040] In the rolling granulation method, it is preferable to use a binder to facilitate the support of the powder of catalytically active components on the carrier and to improve the strength of the produced catalyst. The carrier used in the rolling granulation method includes spherical carriers such as silica, silicon carbide, alumina, mullite, and alundum, each having a major axis diameter of preferably 2.5 mm to 10 mm, and more preferably 2.5 mm to 6 mm. The porosity of the carrier is preferably 20% to 60%, more preferably 30% to 57%, and even more preferably 40% to 55%. The water absorption of the carrier is preferably 10% to 60%, more preferably 12% to 50%, and even more preferably 15% to 40%. By setting the porosity and water absorption rate of the support within the above ranges, the catalytically active component can be easily supported on the support, the cumulative pore volume (A) of the produced catalyst is likely to fall within the range of the present invention, and the ratio (A / B) of the cumulative pore volume (A) to the cumulative pore volume (B) of the pulverized product obtained by pulverizing the catalyst can be easily adjusted within the range of the present invention.

[0041] The tumbling granulation method is a method in which, for example, a disk having a flat or uneven surface is rotated at high speed in a granulator at the bottom of a fixed container, and the carrier in the container is vigorously stirred by repeated rotation and revolution, and a powder of a catalytically active component, and preferably additives such as a binder, a molding aid, and a strength-improving material, are added to the container, thereby supporting the powder of the catalytically active component on the carrier. Examples of methods for adding additives include (1) mixing the catalytically active component powder with the additive to prepare a homogeneous mixture, then feeding the homogeneous mixture into a granulator and stirring; (2) simultaneously feeding the catalytically active component powder and the additive into a granulator and stirring; (3) stirring the catalytically active component powder in a granulator, then feeding the additive into the granulator and stirring again; (4) adding the additive to the catalytically active component powder to prepare a heterogeneous mixture, then feeding the heterogeneous mixture into a granulator and stirring; and (5) dividing the catalytically active component powder and the additive into separate portions and stirring them simultaneously, alternately, or in any order while feeding them into a granulator. Methods such as combining (1) to (5) and adding the entire amount can be arbitrarily employed. Among these, method (5) is preferably performed by adjusting the addition rate using an autofeeder or the like so that the desired amount is supported on the carrier without adhesion of the catalytically active component powder to the wall of the fixed container or aggregation of the catalytically active component powder. In addition, (5) is particularly preferred in that the cumulative pore volume (A) of the produced catalyst is likely to fall within the range of the present invention, and the ratio (A / B) of the cumulative pore volume (A) to the cumulative pore volume (B) of the pulverized product obtained by pulverizing the catalyst is easily adjusted to fall within the range of the present invention.

[0042] Examples of binders include organic binders such as ethanol, glycerin, and polyvinyl alcohol, and inorganic binders such as silica sol aqueous solutions. Organic binders are preferred, with glycerin and polyvinyl alcohol being more preferred, and glycerin being particularly preferred. Organic binders may be used as is, but from the standpoint of workability, they are preferably used as an aqueous solution. The concentration of the aqueous solution is typically 0.1% by weight or more, preferably 2% to 50% by weight, more preferably 3% to 50% by weight, even more preferably 5% to 50% by weight, and particularly preferably 7% to 50% by weight. The amount of binder used is typically 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, per 100 parts by weight of the catalytically active component powder. It is preferably 1% to 40% by weight, more preferably 2% to 35% by weight, even more preferably 7% to 30% by weight, and particularly preferably 10% to 28% by weight relative to the catalyst. By using a binder, particularly an organic binder, at the above aqueous solution concentration and in the above amount, the cumulative pore volume (A) of the produced catalyst is likely to fall within the range of the present invention, and it is also easy to adjust the ratio (A / B) of the cumulative pore volume (A) to the cumulative pore volume (B) of the pulverized product obtained by pulverizing the catalyst to fall within the range of the present invention.

[0043] Examples of molding aids include silica, diatomaceous earth, alumina, glass, and cellulose powder. These may be used alone or in combination, and it is preferable to use a combination of several types. The amount of molding aid used is usually 1 to 20 parts by weight per 100 parts by weight of the powder of the catalytically active component. Furthermore, if necessary, the use of a strength improver such as inorganic fibers such as ceramic fibers and whiskers is useful for improving the strength of the catalyst. The amount of strength improver used is usually 0.5 to 20 parts by weight per 100 parts by weight of the powder of the catalytically active component.

[0044] In the tumbling granulation method, granulation under a high load is preferred in order to ensure that the cumulative pore volume (A) of the pores in the catalyst having a pore diameter of 1 μm or more and 100 μm or less is within a specific range, and that the ratio (A / B) of the cumulative pore volume (A) of the pulverized product obtained by pulverizing the catalyst to the cumulative pore volume (B) of the pores having a pore diameter of 1 μm or more and 100 μm or less of the pulverized product obtained by pulverizing the catalyst is within a specific range. The high load means that the collision strength between the catalytically active component powder and the carrier is increased when the catalytically active component powder is supported on the carrier, and the adhesion strength between the catalytically active component powder and the carrier is increased. As a result, it is believed that the catalytically active component will not penetrate into the pores of the support as much, making it possible to set the ratio (A / B) within a specific range and the cumulative pore volume (A) within a specific range.

[0045] Furthermore, the granulation time depends on the granulation scale; the larger the granulation scale, the longer the required time. The following order of preference is gradually increased: 1 minute to 140 minutes, 1 minute to 130 minutes, 1 minute to 120 minutes, 1 minute to 110 minutes, 1 minute to 100 minutes, 1 minute to 95 minutes, 1 minute to 90 minutes, 1 minute to 85 minutes, 1 minute to 80 minutes, 1 minute to 70 minutes, 1 minute to 60 minutes, 1 minute to 50 minutes, and 1 minute to 40 minutes. By setting the granulation time within the above range, it is possible to set the ratio (A / B) within a specific range. Furthermore, by setting the upper limit of the granulation time within the above range, excessive consolidation of the catalyst surface can be prevented, thereby preventing the cumulative pore volume (A) of the catalyst from becoming smaller, and it is possible to set the cumulative pore volume (A) within a specific range.

[0046] In the tumbling granulation method, if the granulation conditions are set at a high load, the catalytically active components are concentrated on the surface of the carrier, which makes it possible to shorten the granulation time and, as a result, make it possible to make the catalyst packed layer in the fixed-bed reactor thinner.

[0047] Furthermore, in order to control the cumulative pore volume (A) of the pores in the catalyst with a diameter of 1 μm or more and 100 μm or less, it is important to understand the affinity between the support and the powder of the catalytically active component. Supports generally have high water absorption, or so-called hydrophilicity. If the powder of the catalytically active component has the same degree of hydrophilicity, the powder of the catalytically active component will easily penetrate into the pores of the support, making it difficult to control the cumulative pore volume. Therefore, by appropriately selecting a compound with low solubility in water as the source compound in step (a) and adjusting the hydrophilicity of the powder of the catalytically active component, it becomes possible to control the penetration of the powder of the catalytically active component into the support. Examples of source compounds with low solubility in water include bismuth subcarbonate and bismuth oxide.

[0048] The carrier used in the tableting method is silica, silicon carbide, alumina, mullite, alundum, etc., and the size of the carrier is preferably similar to that of the powder of the catalytically active component. Furthermore, it is preferable to use a binder and a molding aid to facilitate the loading of the powder of the catalytically active component on the carrier and to improve the mechanical strength of the produced catalyst. Furthermore, it is preferable to use a pore-imparting agent, which makes it possible to control the cumulative pore volume (A) of pores having a diameter of 1 μm or more and 100 μm or less in the produced catalyst. In the tableting method, it is preferable to thoroughly mix the binder, pore-imparting agent, etc. with the powder of the catalytically active component, etc., before molding to form a compact.

[0049] The binder and molding aid used in the tableting method are preferably the same as the binder and molding aid used in the tumbling granulation method, in the same manner and in the same amount. Examples of pore-imparting agents include organic compounds, and cellulose powder, polyvinyl alcohol, and glycerin are preferably used. When the molded powder is fired, the pore-imparting agent is exposed to high temperatures and decomposed and / or burned, and is released from the molded powder, forming pores. In the tableting method, it is preferable to lower the pressure during tableting in order to control the cumulative pore volume (A) of pores having a diameter of 1 μm or more and 100 μm or less in the catalyst. However, it is important to set an appropriate pressure in consideration of the strength of the produced catalyst.

[0050] The formed body of the catalytically active component powder in step (b) is then dried and calcined to obtain a catalyst. During calcination, the pore-imparting agent is released from the catalyst particles by evaporation or combustion, forming pores within the catalyst particles. The calcination temperature is usually 250°C to 800°C, preferably 300°C to 600°C, and the calcination time is 1 hour to 50 hours. The calcination step is preferably carried out under air flow in order to quickly remove the pore-imparting agent released from the catalyst particles. This makes it possible to obtain a catalyst with high strength while forming many pores. Furthermore, gas generated from the catalyst particles is quickly removed and air is supplied to the catalyst particles, thereby enabling the production of a uniformly calcined catalyst. If the air flow is insufficient, the catalyst is destroyed by the pressure change that occurs when the pore-imparting agent is released, resulting in a decrease in strength and a decrease in the conversion rate, selectivity for unsaturated aldehyde, and selectivity for unsaturated carboxylic acid.

[0051] The catalyst thus produced is supplied to a fixed-bed reactor and used in the reaction of producing unsaturated aldehydes and unsaturated carboxylic acids such as acrolein and acrylic acid by gas-phase catalytic oxidation of an olefin such as propylene with an oxygen-containing gas. The content of the olefin in the gas supplied to the fixed-bed reactor is preferably in the range of 5% by volume to 15% by volume, and the space velocity of the olefin is preferably 50 h -1 ~320h -1 The range is preferably 80h -1 ~320h -1 The range is more preferable. The space velocity is a value expressed by the following formula. ·Space velocity SV(h -1 ) = Volumetric flow rate of olefin gas supplied to the reactor (0°C, 1 atmosphere) / Volume of catalyst packed in the reactor (not including non-reactive solids)

[0052] For example, the reaction of producing acrolein and acrylic acid by gas-phase catalytic oxidation of propylene and an oxygen-containing gas is carried out by supplying a gas having a composition of 5% to 15% by volume of propylene, 5% to 18% by volume of molecular oxygen, 0 to 40% by volume of steam, and 20% to 70% by volume of an inert gas, such as nitrogen or carbon dioxide, to a fixed-bed reactor packed with the catalyst produced as described above. Preferred reaction conditions are a temperature range of 300°C to 450°C, a pressure of atmospheric pressure to 150 kPa, and a contact time with the catalyst of 0.5 to 5 seconds. [Example]

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0054] <Measurement of loading rate> Thirty particles of catalyst were sampled and the total weight was measured (weight A). Thirty particles of support were sampled and the total weight was measured (weight B). The loading rate was calculated using the following formula. Loading rate (%) = (weight A - weight B) / weight A x 100

[0055] <Measurement of pore distribution spectrum and cumulative pore volume> Using an Autopore IV9520 model manufactured by Micromeritics Japan (same company), the sample was subjected to reduced pressure treatment (50 μmHg or less) for 10 minutes, and the cumulative pore volume of pores with diameters of 1 μm to 100 μm was measured from the mercury intrusion / extrusion curve.

[0056] <Measurement of major axis diameter, minor axis diameter, and average diameter of catalyst> One hundred catalyst particles were sampled, and the major axis diameter, minor axis diameter, and average diameter of each particle were measured using a high-precision two-dimensional size measuring instrument VM-8040 manufactured by Keyence Corporation. The average major axis diameter, minor axis diameter, and average diameter of the 100 particles were then calculated. Furthermore, the ratio of the average major axis diameter to the average minor axis diameter was calculated to evaluate the shape of the catalyst.

[0057] <Measurement of catalyst powdering rate> The catalyst was sieved through a sieve with 2.36 mm openings, and the particles remaining on the sieve were used as the sample for measuring the powder rate. A funnel (conical upper diameter: 150 mm, conical lower diameter: 25 mm) was inserted into the top of a 1 m high acrylic cylinder (φ66 mm), and a tray was placed at the bottom of the cylinder. Approximately 20 g of the sample for measuring the powder rate was precisely weighed and placed into the conical top of the funnel, and allowed to fall through the cylinder into the tray. The dropped sample for measuring the powder rate was recovered from the tray, and the weight of the fine particles sieved through the 2.36 mm openings (powdered weight) was measured, and the catalyst powder rate was calculated using the following formula. Powdering rate (%) = (powdered weight / weight of sample for powdering rate measurement) x 100

[0058] Example 1 <Catalyst Preparation> A catalytically active component was prepared by the method described in the examples of JP 2017-176931 A. The catalytically active component was calcined at 440°C for 6 hours in an air atmosphere and pulverized, and 100 parts by weight of the catalytically active component was mixed with 5 parts by weight of cellulose and 5 parts by weight of glass powder as molding aids to obtain a powder containing the catalytically active component (hereinafter referred to as "Powder A").

[0059] A supported molded body was prepared by tumbling granulation using powder A, a 30 wt% aqueous solution of glycerin, and a spherical carrier composed primarily of alumina and silica. Specifically, 150 g of a 4.0 mm diameter spherical carrier (porosity 50%, water absorption 20%) was placed in a Dalton Marumerizer QJ-230T-2 (cylinder diameter 23 cm) and rotated at 150 rpm. Powder A and the glycerin aqueous solution were then alternately added repeatedly for 16 minutes to support powder A on the carrier, yielding a supported molded body. The amount of glycerin aqueous solution used was 71 parts by weight per 100 parts by weight of powder A. The supported molded body was dried and calcined in a cylindrical container under air flow at 505°C for 2 hours to obtain catalyst A. The ratio of the mean major axis diameter to the mean minor axis diameter of catalyst A was 1.095, and the shape of the catalyst was determined to be spherical, with an average diameter of 5.53 mm. The powdering rate of catalyst A was measured, and the results are summarized in Table 1. The cumulative pore volume (A) of pores having a diameter of 1 μm or more and 100 μm or less in catalyst A was 0.174 ml / g. The loading rate of catalyst A was 54%. The atomic ratios of catalytically active elements in catalyst A were as follows: Mo / Bi / Co / Ni / Fe=12 / 2.9 / 3.4 / 3.4 / 0.8

[0060] <Crushing of catalyst A> 100 g of the catalyst A was placed in a Dalton Corporation Marumerizer QJ-230T-2 model (cylinder diameter 23 cm), and operation was started at 300 rpm. The speed was gradually increased to 1000 rpm over 1 minute, and the mixture was pulverized for 2 minutes. After operation was stopped, the clumps remaining in the Marumerizer's cylindrical portion were removed and sieved through a Tyler 6 mesh. The pulverized material on the sieve had an integrated pore volume (B) of pores with a pore diameter of 1 μm or more and 100 μm or less, and was found to be 0.213 ml / g. From the above, the ratio (A / B) of the integrated pore volume (A) to the integrated pore volume (B) was 0.82.

[0061] <Gas-phase catalytic oxidation of propylene> 40 ml of the catalyst A was mixed with 52 ml of mullite balls and packed into a stainless steel reactor tube with a niter jacket. A raw material gas mixture of 10% by volume of propylene, 17% by volume of steam, 15% by volume of oxygen, and 58% by volume of nitrogen was introduced into the reactor tube at a pressure of 70 kPa to carry out the oxidation reaction of propylene. At this time, the space velocity of propylene was 100 h -1 The results are summarized in Table 1.

[0062] Here, the definitions of propylene conversion rate and (acrolein + acrylic acid) selectivity are as follows. Propylene conversion rate (mol%) = (number of moles of reacted propylene / number of moles of supplied propylene) × 100 Acrolein selectivity (mol%) = (moles of acrolein produced / moles of propylene reacted) x 100 Acrylic acid selectivity (mol%) = (moles of acrylic acid produced / moles of propylene reacted) x 100

[0063] Example 2 A catalytically active component was prepared by the method described in the examples of JP 2017-176931 A. Without calcining or pulverizing the catalytically active component, 100 parts by weight of the catalytically active component was mixed with 5 parts by weight of cellulose and 5 parts by weight of glass powder as molding aids to obtain a powder containing the catalytically active component (hereinafter referred to as "powder B"). A supported molded body was prepared by tumbling granulation using powder B, a 30 wt% aqueous solution of glycerin, and a carrier primarily composed of alumina and silica. Specifically, 5 kg of spherical carriers (50% porosity, 20% water absorption) with a diameter of 4.0 mm were placed in a pan-type tumbling granulator with a cylindrical diameter of 58 cm, and rotated at 30 rpm with the bottom tilted 45 degrees from the horizontal position. Powder B and the glycerin aqueous solution were then alternately added repeatedly for 80 minutes to support powder B on the carrier, yielding a supported molded body. The amount of glycerin aqueous solution used was 34 parts by weight per 100 parts by weight of powder B. The supported molded body was dried and calcined in a cylindrical container under air flow at 505°C for 2 hours to obtain catalyst B. The ratio of the mean major axis diameter to the mean minor axis diameter of catalyst B was 1.071, and the shape of the catalyst was determined to be spherical, with an average diameter of 5.40 mm. The powdering rate of catalyst B was measured, and the results are summarized in Table 1. The cumulative pore volume (A) of pores having a diameter of 1 μm or more and 100 μm or less in catalyst B was 0.135 ml / g. The loading rate of catalyst B was 54%. The atomic ratios of catalytically active elements in catalyst B were as follows: Mo / Bi / Co / Ni / Fe=12 / 2.9 / 3.4 / 3.4 / 0.8

[0064] The catalyst B was crushed under the same conditions as in Example 1. The cumulative pore volume (B) of the crushed product on the sieve, which had pores with diameters of 1 μm or more and 100 μm or less, was 0.210 ml / g. From the above, the ratio (A / B) of the cumulative pore volume (A) to the cumulative pore volume (B) was 0.64. Using this catalyst B, a propylene oxidation reaction was carried out under the same conditions as in Example 1. The results are summarized in Table 1.

[0065] Example 3 Using powder A prepared in Example 1, a 30 wt % aqueous solution of glycerin, and a carrier containing alumina and silica as main components, a supported molded body was prepared by the tumbling granulation method under the conditions described in Example 1. The amount of carrier used was 500 g, the amount of glycerin aqueous solution was 56 parts by weight relative to 100 parts by weight of powder A, and the granulation time was 30 minutes. The supported molded body was dried and calcined in a cylindrical container under air flow at 505°C for 2 hours to obtain catalyst C. The ratio of the mean major axis diameter to the mean minor axis diameter of catalyst C was 1.070, and the shape of the catalyst was determined to be spherical, with an average diameter of 5.48 mm. The powdering rate of catalyst C was measured, and the results are summarized in Table 1. The cumulative pore volume (A) of pores having a diameter of 1 μm or more and 100 μm or less in catalyst C was 0.145 ml / g. The loading rate of catalyst C was 55%. The atomic ratios of catalytically active elements in catalyst C were as follows: Mo / Bi / Co / Ni / Fe=12 / 2.9 / 3.4 / 3.4 / 0.8

[0066] The catalyst C was crushed under the same conditions as in Example 1. The cumulative pore volume (B) of the crushed product on the sieve, which had pores with diameters of 1 μm or more and 100 μm or less, was 0.215 ml / g. From the above, the ratio (A / B) of the cumulative pore volume (A) to the cumulative pore volume (B) was 0.67. Using this catalyst C, a propylene oxidation reaction was carried out under the same conditions as in Example 1. The results are summarized in Table 1.

[0067] (Comparative Example 1) Using powder A prepared in Example 1, a 30 wt % aqueous solution of glycerin, and a carrier containing alumina and silica as main components, a supported molded body was prepared by the tumbling granulation method under the conditions described in Example 2. The amount of carrier used was 10 kg, the amount of glycerin aqueous solution was 31 parts by weight relative to 100 parts by weight of powder A, and the granulation time was 140 minutes. The supported molded body was dried and calcined in a cylindrical container under air flow at 505°C for 2 hours to obtain catalyst D. The ratio of the mean major axis diameter to the mean minor axis diameter of catalyst D was 1.068, and the shape of the catalyst was determined to be spherical, with an average diameter of 5.44 mm. The powdering rate of catalyst D was measured, and the results are summarized in Table 1. The cumulative pore volume (A) of pores having a diameter of 1 μm or more and 100 μm or less in catalyst D was 0.046 ml / g. The loading rate of catalyst D was 57%. The atomic ratios of catalytically active elements in catalyst D were as follows: Mo / Bi / Co / Ni / Fe=12 / 2.9 / 3.4 / 3.4 / 0.8

[0068] Catalyst D was crushed under the same conditions as in Example 1. The pulverized product on the sieve had an integrated pore volume (B) of pores with a pore diameter of 1 μm or more and 100 μm or less, of 0.208 ml / g. From the above, the ratio (A / B) of the integrated pore volume (A) to the integrated pore volume (B) was 0.22. Using this catalyst D, a propylene oxidation reaction was carried out under the same conditions as in Example 1. The results are summarized in Table 1.

[0069] (Comparative Example 2) Using powder A prepared in Example 1, a 30 wt % aqueous solution of glycerin, and a carrier containing alumina and silica as main components, a supported molded body was prepared by the tumbling granulation method under the conditions described in Example 1. The amount of carrier used was 200 g, the amount of glycerin aqueous solution was 61 parts by weight relative to 100 parts by weight of powder A, and the granulation time was 15 minutes. The supported molded body was dried and calcined in a sagger placed in a muffle furnace at 505°C for 2 hours to obtain catalyst E. The ratio of the mean major axis diameter to the mean minor axis diameter of catalyst E was 1.079, indicating that the shape of the catalyst was spherical, with an average diameter of 5.54 mm. The powdering rate of catalyst E was measured, and the results are summarized in Table 1. The cumulative pore volume (A) of pores having a diameter of 1 μm or more and 100 μm or less in catalyst E was 0.191 ml / g. The loading rate of catalyst E was 54%. The atomic ratios of catalytically active elements in catalyst E were as follows: Mo / Bi / Co / Ni / Fe=12 / 2.9 / 3.4 / 3.4 / 0.8

[0070] Catalyst E was crushed under the same conditions as in Example 1. The pulverized product on the sieve had an integrated pore volume (B) of pores with a diameter of 1 μm or more and 100 μm or less, of 0.216 ml / g. From the above, the ratio (A / B) of the integrated pore volume (A) to the integrated pore volume (B) was 0.88. Using this catalyst E, a propylene oxidation reaction was carried out under the same conditions as in Example 1. The results are summarized in Table 1.

[0071] [Table 1]

Claims

1. A catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids, comprising: The catalyst has an integrated pore volume (A) of pores having a pore diameter of 1 μm or more and 100 μm or less of 0.12 ml / g or more and 0.18 ml / g or less, and A catalyst in which, among the pulverized products obtained by pulverizing the catalyst under pulverization conditions A, the pulverized products that do not pass through a Tyler 6 mesh have an integrated pore volume (A) of pores having a pore diameter of 1 μm or more and 100 μm or less to an integrated pore volume (B) of the pulverized products, the ratio (A / B) of the integrated pore volume (A) to the integrated pore volume (B) of pores having a pore diameter of 1 μm or more and 100 μm or less is 0.30 or more and 0.87 or less (Pulverization conditions A). 100 g of the catalyst was placed into a tumbling granulator in which a cylinder was fixed vertically, a disk was installed horizontally at the bottom end of the cylinder, and the disk rotated around the center of the cylinder, causing the particles to rotate and revolve about their own axis. The disk was then started to operate at a relative centrifugal acceleration of 12 G, and after 1 minute, the relative centrifugal acceleration was increased to 130 G, and the disk was continued to rotate at the relative centrifugal acceleration of 130 G for 2 minutes. The relative centrifugal acceleration is a numerical value that expresses the magnitude of the centrifugal force acting per unit weight of the catalyst as a ratio to the acceleration of gravity, and is expressed by the following formula (X): F = 1118 × r × N ２ ×10 －８ Formula (X) F: relative centrifugal acceleration (G), r: distance from the center of rotation to the bottom of the cylinder (cm) N: rotation speed (rpm)

2. The catalyst according to claim 1, wherein the ratio (A / B) is 0.30 or more and 0.82 or less.

3. A catalyst according to claim 1 or 2, comprising molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni) and iron (Fe), and wherein the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni) and iron (Fe) in the catalyst satisfies the following formula (1): Mo ａ Yes ｂ Yes ｃ Yes ｄ Fe ｅ (1) (wherein a to e represent the atomic ratio of each element, when a = 12, b = 0.5 to 7, c = 0.1 to 10, d = 0.1 to 10, e = 0.05 to 5.

4. The catalyst of any one of claims 1 to 3, wherein the catalyst comprises a support.

5. The catalyst according to any one of claims 1 to 4, wherein the catalyst has a spherical shape.

6. A method for producing acrolein and acrylic acid, comprising a step of gas-phase catalytic oxidation of propylene and an oxygen-containing gas using the catalyst according to any one of claims 1 to 5.

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