Method for producing unsaturated aldehyde compounds or unsaturated carboxylic acid compounds

Abstract

This invention provides a method for producing a corresponding unsaturated aldehyde compound or unsaturated carboxylic acid compound by gas-phase catalytic oxidation of an alkene with molecular oxygen or a molecular oxygen-containing gas. [Solution] A method for producing an unsaturated aldehyde compound or an unsaturated carboxylic acid compound using a fixed-bed multitube reactor having multiple reaction tubes, wherein the reaction tubes are provided with two or more catalyst layers in the gas flow direction, and the atomic ratio A1 of cerium element to molybdenum element contained in the catalytic active component of the catalyst packed in the first layer from the raw material gas inlet, and the atomic ratio A of cerium element to molybdenum element contained in the catalytic active component of the catalyst packed in the kth layer, which is any layer from the second layer onwards from the raw material gas inlet. k This invention relates to a method for producing an unsaturated aldehyde compound or an unsaturated carboxylic acid compound that satisfies the relationship shown in formula (1) below. A1-A k >0(1)

Description

[Technical Field]

[0001] The present invention relates to a method for producing a corresponding unsaturated aldehyde compound or unsaturated carboxylic acid compound by gas-phase catalytic oxidation of an alkene with molecular oxygen or a molecular oxygen-containing gas. [Background technology]

[0002] Methods for producing acrolein, methacrolein, and methacrylic acid using propylene, isobutylene, t-butyl alcohol, etc., as raw materials are widely implemented industrially. Furthermore, many reports have been made on means of improving the yield of these production methods (for example, Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2016 / 136882 [Patent Document 2] Japanese Patent Application Publication No. 2017-024009 [Patent Document 3] Chinese Patent Application Publication No. 115260015 Specification [Patent Document 4] Japanese Patent Application Publication No. 2023-141551 [Patent Document 5] International Publication No. 2014 / 051090 [Patent Document 6] Japanese Patent Publication No. 2003-146920 [Overview of the project] [Problems that the invention aims to solve]

[0004] Even with the improvements described above, further yield improvements are needed in the production of methacrolein and / or methacrylic acid through the partial oxidation reaction of isobutylene, t-butyl alcohol, etc. This is because the yield of the target product greatly affects the amount of isobutylene, t-butyl alcohol, etc. required for production, and thus significantly impacts production costs. Furthermore, continuing operation at low yields generates large amounts of by-products, placing a heavy burden on the purification process and increasing the time and operating costs of the purification process. Moreover, depending on the type of by-product, it may accumulate on the catalyst surface or in the gas flow path near the catalyst. The accumulated by-products cover the necessary reaction active sites on the catalyst surface, reducing the catalyst's activity, so the reaction bath temperature must be increased to forcibly increase the activity. This causes thermal stress on the catalyst, leading to a decrease in its lifespan and further reduction in selectivity, resulting in a decrease in yield. In addition, the accumulation of by-products in the system can cause an increase in system pressure, which can also reduce selectivity and lead to a decrease in yield. In the worst case, a sudden increase in internal pressure could cause a temperature anomaly and the reaction could run out of control. In that case, it is conceivable that the system would need to be shut down for an extended period, requiring system cleaning and catalyst replacement.

[0005] For example, Patent Document 3 describes a method for improving yield by making the upper layer highly selective and the lower layer highly active in a catalyst packing package. However, even with this method, the yield improvement is not sufficient, and further improvement is required.

[0006] Patent Document 4 describes that by increasing the amount of active ingredient in the upper layer and decreasing the amount of active ingredient in the lower layer of a catalyst packing package, high yields can be maintained even in regions with high raw material conversion rates. However, even with this method, it is difficult to maintain high yields in the long term, and further improvements are needed.

[0007] Patent Document 5 describes how increasing the ratio of iron and bismuth in a cerium-containing catalyst in a method for producing unsaturated nitriles improves the redox ability by generating a specific crystalline phase. However, even with these methods, the yield and catalyst lifetime were insufficient, making it difficult to maintain a high yield over the long term. Therefore, a catalyst with even higher yield is desired.

[0008] Furthermore, Patent Document 6 describes a method for producing acrolein in which the target product can be obtained in high yield over the long term by adjusting the Fe / (Co+Ni) or Co / (Co+Ni) in the catalyst. However, in the production of methacrolein, which produces many by-products during the reaction, it is difficult to maintain high yield over the long term even with this method, and further improvements are needed.

[0009] This invention provides a gas-phase catalytic oxidation method for producing corresponding unsaturated aldehydes and unsaturated carboxylic acids using propylene, isobutylene, t-butyl alcohol, etc., as raw materials, and proposes a production method that maintains a high yield of the target product over the long term, even in regions with high raw material conversion rates. [Means for solving the problem]

[0010] As a result of diligent research under these circumstances, the inventors have found that the above problems can be solved by adopting a novel method in which a fixed-bed multitubular reactor is divided and multiple reaction zones are provided for filling with catalysts, and two or more types of catalysts with different ratios of cerium to molybdenum in the catalytic active components of the catalysts filled in the first and second layers from the raw material gas inlet are filled in such a way that a specific relationship is satisfied.

[0011] In other words, the present invention relates to the following 1) to 8). 1) A method for producing an unsaturated aldehyde compound or an unsaturated carboxylic acid compound using a fixed-bed multitubular reactor having multiple reaction tubes, Two or more catalyst layers are provided in the reaction tube in the gas flow direction, the atomic ratio A1 of cerium element to molybdenum element contained in the catalytically active component of the catalyst packed in the first layer from the raw material gas inlet portion, and the atomic ratio A of cerium element to molybdenum element contained in the catalytically active component of the catalyst packed in the k-th layer, which is any one of the second and subsequent layers from the raw material gas inlet portion k satisfy the relationship of the following formula (1), A1-A k >0 (1) A method for producing an unsaturated aldehyde compound or an unsaturated carboxylic acid compound. 2) the atomic ratio B1 of iron element to molybdenum element contained in the catalytically active component of the catalyst packed in the first layer from the raw material gas inlet portion, and the atomic ratio B of iron element to molybdenum element contained in the catalytically active component of the catalyst packed in the k-th layer k satisfy the relationship of the following formula (2), B k -B1>0 (2) The production method according to 1). 3) the sum (A1+B1) of the atomic ratio A1 of cerium element to molybdenum element and the atomic ratio B1 of iron element contained in the catalytically active component of the catalyst packed in the first layer from the raw material gas inlet portion, and the atomic ratio A of cerium element to molybdenum element contained in the catalytically active component of the catalyst packed in the k-th layer k and the atomic ratio B of iron element k the sum (A k +B k ) satisfy the relationship of the following formula (3), (A k +B k )-(A1+B1)>0 (3) The production method according to 1) or 2). 4) The catalyst packed in the first layer from the raw material gas inlet portion has a catalytically active component having a composition represented by the following formula (4), the production method according to any one of 1) to 3). [Formula 1] Mo a1 Bi b1 Nic1 Co d1 Fe e1 Ce f1 X g1 Y h1 Z i1 O j1 ···(4) In the formula, Mo, Bi, Ni, Co, Fe and Ce represent molybdenum, bismuth, nickel, cobalt, iron and cerium respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum and titanium, Y represents at least one element selected from sodium, potassium, cesium, rubidium and thallium, Z represents at least one element that belongs to Groups 1 to 16 of the periodic table and is selected from elements other than the above Mo, Bi, Ni, Co, Fe, Ce, X and Y, and a1, b1, c1, d1, e1, f1, g1, h1, i1 and j1 represent the atomic numbers of molybdenum, bismuth, nickel, cobalt, iron, cerium, X, Y, Z and oxygen respectively, and when a1=12, 1.5<b1≦7.0, 0≦c1≦10.0, 0≦d1≦8.0, 0.0≦c1+d1≦17.0, 0<e1≦1.8, 0<f1≦2.0, 0≦g1≦3.0, 0≦h1≦5.0, 0≦i1≦5.0, and j1 is a value determined by the oxidation state of each element. 5) The production method according to any one of 4), wherein the catalyst packed in the first layer from the raw material gas inlet part has a catalytically active component having a composition in which, when a1=12 in the above formula (4), the range of b1 is 1.8≦b1≦2.4, the range of c1 is 0.3≦c1≦1.6, the range of d1 is 4.8≦d1≦8.0, the range of c1+d1 is 5.2≦c1+d1≦9.5, the range of e1 is 0.8≦e1≦1.2, the range of f1 is 0.3≦f1≦1.6, g1 is 0, the range of h1 is 0.12≦h1≦0.25, and i1 is 0. 6) The production method according to any one of 1) to 5), wherein the supported rate of the catalyst packed in the first layer from the raw material gas inlet part is 35% or more and 55% or less. 7) A manufacturing method according to any one of items 1) to 6), wherein the particle size of the catalyst packed in the first layer from the raw material gas inlet is 4.1 mm or more and 5.0 mm or less. 8) The method for producing a product according to any one of claims 1) to 7), wherein the unsaturated aldehyde compound is methacrolein and the unsaturated carboxylic acid compound is methacrylic acid. [Effects of the Invention]

[0012] The production method of the present invention is highly effective in improving yield in gas-phase catalytic oxidation reactions and is useful when producing corresponding unsaturated aldehydes and unsaturated carboxylic acids using propylene, isobutylene, t-butyl alcohol, etc., as raw materials. This method is particularly effective when producing corresponding unsaturated aldehydes using propylene, isobutylene, t-butyl alcohol, etc., as raw materials, especially in the reaction to obtain methacrolein by gas-phase catalytic oxidation of isobutylene. Using the production method of the present invention in the gas-phase catalytic oxidation reaction of isobutylene also contributes to improving yield in regions with high raw material conversion rates. This is a particularly effective feature in direct acid methods where isobutylene becomes the toxic substance in the subsequent reaction. [Modes for carrying out the invention]

[0013] [Catalyst layer] The present invention relates to a method for producing unsaturated aldehydes or unsaturated carboxylic acids (hereinafter also simply referred to as the production method), which involves filling reaction tubes in a fixed-bed multitubular reactor with two or more catalyst layers. In this specification, this state is expressed as dividing the catalyst layer into n sections, where n is an integer of 2 or more. That is, dividing the catalyst layer into n sections means constructing n catalyst layers in the reaction tube. There are no particular restrictions on n as long as it is 2 or greater, and it can be set appropriately with a guideline of about 10 considering the equipment conditions and catalyst selection, but it is preferable to set it to 2 or 3, and more preferably to 2. Furthermore, the catalysts in each layer differ from each other in one or more respects of the type of catalytically active component, the density of catalytically active components, the catalyst particle size, and the dilution rate by the inert carrier, as described below, but when n is 3 or greater, this does not exclude the case in which the same catalyst is used in non-adjacent layers. In this specification, the catalyst layer is defined as the first layer containing the catalytically active component at the raw material gas inlet, and the nth layer at the raw material gas outlet.

[0014] In this invention, two or more catalysts with different component ratios of cerium (hereinafter also referred to as cerium) to molybdenum (hereinafter also referred to as molybdenum) are packed into the catalyst layers of the reactor, which is divided into two or more sections as described above. In particular, the component ratio A1 of cerium to molybdenum contained in the catalytic active component of the catalyst packed into the first layer from the raw material gas inlet and the component ratio A of cerium to molybdenum contained in the catalytic active component of the catalyst packed into the k-th layer (2≦k≦n), which is any layer from the second layer onward from the raw material gas inlet. k The filling method is not limited if the relationship is as shown in equation (1) below. A1-A k >0 (1) Furthermore, a packing method is preferred in which the ratio of cerium to molybdenum in the catalyst decreases from the raw material gas inlet to the outlet. For example, in the case of n=2, two types of catalysts with different atomic ratios of cerium to molybdenum are prepared, and the catalysts are packed in such a way that the ratio of cerium to molybdenum in the catalyst packed in the catalyst layer on the raw material gas outlet side (hereinafter sometimes referred to as the lower layer) is smaller than the ratio of cerium to molybdenum in the catalyst packed in the catalyst layer on the raw material gas inlet side (hereinafter sometimes referred to as the upper layer). In other words, it is preferable that the upper layer is filled with a catalyst having a relatively high cerium-to-molybdenum ratio, and the lower layer is filled with a catalyst having a relatively low cerium-to-molybdenum ratio compared to the upper layer. Unless otherwise specified in this application, "relative to molybdenum" means when the elemental value of molybdenum is set to 12. Component ratio refers to atomic ratio.

[0015] The ratio of cerium to molybdenum in the catalytic active component of the catalyst packed in the first layer from the raw material gas inlet (A1) and the ratio of cerium to molybdenum in the catalytic active component of the catalyst packed in the k-th layer, which is any layer from the second layer onwards from the raw material gas inlet (A) k The relationship (A1-A k ) is preferably greater than 0, but more preferably as a lower limit, it is 0.01, 0.1, and 0.2, in order, and particularly preferably 0.3. A1 and A k The relationship (A1-A k (A1-A) is preferably 2 or less, and more preferably as upper limits are 1.5, 1.0, 0.9, 0.8, and 0.7, in that order, with 0.6 being particularly preferred. k The preferred range of ) is greater than 0 and 2.0 or less, more preferably greater than 0 and 1.5 or less, more preferably greater than 0 and 1.0 or less, more preferably greater than 0 and 0.9 or less, more preferably greater than 0 and 0.8 or less, more preferably greater than 0 and 0.7 or less, more preferably greater than 0 and 0.6 or less, more preferably 0.01 or more and 0.6 or less, more preferably 0.1 or more and 0.6 or less, more preferably 0.2 or more and 0.6 or less, and particularly preferably 0.3 or more and 0.6 or less.

[0016] Furthermore, in this invention, the component ratio B1 of iron element (hereinafter also referred to as iron) to molybdenum contained in the catalytic active component of the catalyst packed in the first layer from the raw material gas inlet, and the component ratio B of iron to molybdenum contained in the catalytic active component of the catalyst packed in the k-th layer are also specified. k A packing method that satisfies the relationship shown in equation (2) below is more preferable. Here, the k-th layer means the same layer as the k-th layer that satisfies equation (1) above. B k -B1>0 (2) Furthermore, a packing method is preferred in which the ratio of iron to molybdenum in the catalyst increases from the raw material gas inlet to the outlet. For example, when two reaction zones are provided by dividing the reactor, two types of catalysts with different ratios of iron to molybdenum are prepared, and the catalysts are packed in such a way that the ratio of iron to molybdenum in the lower layer is greater than that of the catalyst packed in the upper layer. In other words, it is preferable that the upper layer is filled with a catalyst having a relatively small iron-to-molybdenum ratio, and the lower layer is filled with a catalyst having a relatively large iron-to-molybdenum ratio compared to the upper layer.

[0017] The ratio of iron to molybdenum in the catalytic active component of the catalyst packed in the first layer from the raw gas inlet, B1, and the ratio of iron to molybdenum in the catalytic active component of the catalyst packed in the k-th layer, B k Relationship value (B k -B1) is preferably greater than 0, but more preferably as a lower limit, it is 0.01, 0.1, and 0.3, in order, and particularly preferably 0.4. B1 and B k Relationship value (B k -B1) is preferably 3 or less, and more preferably as upper limits are 2.0, 1.5, 1.2, 1.1, 1.0, and 0.9, in that order, with 0.8 being particularly preferred. Therefore, (B k -B1) is preferably greater than 0 and 3.0 or less, more preferably greater than 0 and 2.0 or less, more preferably greater than 0 and 1.5 or less, more preferably greater than 0 and 1.2 or less, more preferably greater than 0 and 1.1 or less, more preferably greater than 0 and 1.0 or less, more preferably greater than 0 and 0.9 or less, more preferably greater than 0 and 0.8 or less, more preferably 0.01 or more and 0.8 or less, more preferably 0.1 or more and 0.8 or less, more preferably 0.3 or more and 0.8 or less, and particularly preferably 0.4 or more and 0.8 or less.

[0018] Furthermore, in this invention, the sum of the ratio of cerium to molybdenum and the ratio of iron to molybdenum in the catalytic active component of the catalyst packed in the first layer from the raw material gas inlet, A1 and the ratio of cerium to molybdenum in the catalytic active component of the catalyst packed in the k-th layer, A k and iron content ratio B k A packing method that satisfies the relationship between the sum of the layers shown in equation (3) below is more preferable. Here, the k-th layer refers to the same layer as the k-th layer that satisfies equation (1) above. (A k +B k )-(A1+B1)>0 (3) Furthermore, more preferably, a packing method is used such that the sum of the component ratios of cerium and iron relative to molybdenum in the catalyst increases from the raw material gas inlet to the outlet. For example, in the case of n=2, two types of catalysts with different sums of component ratios of cerium and iron relative to molybdenum are prepared, and the catalysts are packed such that the sum of the component ratios of cerium and iron relative to molybdenum in the lower layer of the catalyst is greater than the sum of the component ratios of cerium and iron relative to molybdenum in the upper layer of the catalyst. In other words, it is preferable that the upper layer is filled with a catalyst in which the sum of the component ratios of cerium and iron relative to molybdenum is relatively small, and the lower layer is filled with a catalyst in which the sum of the component ratios of cerium and iron relative to molybdenum is relatively large compared to the upper layer.

[0019] The catalytic active component of the catalyst packed in the first layer from the raw material gas inlet contains the sum of the ratio of cerium to molybdenum and the ratio of iron (A1+B1) and the catalytic active component of the catalyst packed in the above k-th layer contains the sum of the ratio of cerium to molybdenum and the ratio of iron (A k +B k ) Relationship {(A k +B k (A1+B1) and (A k +B k ) Relationship {(A k +B kThe upper limit of {(A)-(A1+B1)} is preferably 3.4 or less, more preferably 3.0, 2.5, 2.0, 1.5, 1.0, 0.8, 0.6, 0.4 in that order from top to bottom, and particularly preferably 0.3. Therefore, {(A k +B k The preferred range of )-(A1+B1) is greater than 0 and 3.4 or less, more preferably greater than 0 and 3.0 or less, more preferably greater than 0 and 2.5 or less, more preferably greater than 0 and 2.0 or less, more preferably greater than 0 and 1.5 or less, more preferably greater than 0 and 1.0 or less, more preferably greater than 0 and 0.8 or less, more preferably greater than 0 and 0.6 or less, more preferably greater than 0 and 0.4 or less, more preferably greater than 0 and 0.3 or less, more preferably 0.01 or more and 0.3 or less, more preferably 0.05 or more and 0.3 or less, more preferably 0.1 or more and 0.3 or less, and particularly preferably 0.15 or more and 0.3 or less.

[0020] Although the detailed mechanism of the present invention is unclear, the inventors surmise the following: Since this reaction is an oxidation reaction, oxygen is consumed and heat is generated as the reaction proceeds. Therefore, the oxygen concentration and catalyst layer temperature are high on the gas inlet side of the reaction tube. On the other hand, the oxygen concentration and catalyst layer temperature tend to be low on the gas outlet side. Here, cerium has the ability to absorb and release oxygen, which can promote the re-oxidation of the catalyst. On the other hand, iron's active species are easily maintained even under low oxygen concentration conditions. Therefore, good performance is achieved by filling the raw material gas inlet side with a catalyst that has a high cerium-to-molybdenum ratio and the raw material gas outlet side with a catalyst that has a high iron-to-molybdenum ratio. As described above, the first layer in the present invention refers to the first catalyst layer counted from the raw material gas inlet side. However, based on the mechanism described above, the catalyst layer with the highest reaction temperature may be considered the first layer. That is, good performance is achieved when the catalyst layer with the highest reaction temperature is considered the first layer, and any of the layers from the second layer onward (i.e., closer to the raw material gas outlet than the first layer) is considered the k-th layer, and equation (1) is satisfied.

[0021] [Catalyst Composition] The catalyst packed in the first layer from the raw material gas inlet part preferably has a catalytically active component having a composition represented by the following formula (4). By using the catalyst having this composition, a by-product reduction effect can also be expected. [Formula 1] Mo a1 Bi b1 Ni c1 Co d1 Fe e1 Ce f1 X g1 Y h1 Z i1 O j1 ···(4) In the formula, Mo, Bi, Ni, Co, Fe and Ce represent molybdenum, bismuth, nickel, cobalt, iron and cerium respectively, X is at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum and titanium, Y is at least one element selected from sodium, potassium, cesium, rubidium, and thallium, Z belongs to Groups 1 to 16 of the periodic table and means at least one element selected from elements other than the above Mo, Bi, Ni, Co, Fe, Ce, X, and Y, a1, b1, c1, d1, e1, f1, g1, h1, i1 and j1 represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, cerium, X, Y, Z and oxygen respectively, and when a1=12, 1.5<b1≦7.0, 0≦c1≦10.0, 0≦d1≦8.0, 0.0≦c1+d1≦17.0, 0<e1≦1.8, 0<f1≦2.0, 0≦g1≦3.0, 0≦h1≦5.0, 0≦i1≦5.0, and j1 is a value determined by the oxidation state of each element.

[0022] In formula (4) above, Z is not particularly limited as long as it is at least one element selected from groups 1 to 16 of the periodic table other than Mo, Bi, Ni, Co, Fe, Ce, X, and Y, but phosphorus (P), calcium (Ca), scandium (Sc), copper (Cu), gallium (Ga), germanium (Ge), arsenic (As), strontium (Sr), yttrium (Y), niobium (Nb), technetium (Tc), indium (In), tellurium (Te), barium (Ba), tantalum (Ta), lanthanum (La), samarium (Sm), and gadolinium (Gd), more preferably P, Ca, Cu, Ga, Sr, Nb, Ba, Ta, La, Sm, and Gd, and particularly preferably Cu and Gd.

[0023] In the manufacturing method of the present invention, the composition of the catalytic active component differs between the raw material gas inlet side and the outlet side. For the catalytic active component on the raw material gas inlet side, i.e., the first layer, the preferred range of b1 to i1 when a1 = 12 in formula (4) above is as follows. The preferred lower limits for b1 are, in order of preference, 0.5, 0.8, 1.1, 1.4, and 1.8, with a particularly preferred value of 1.9. The preferred upper limits are, in order of preference, 6, 4, 3, and 2.5, with a particularly preferred value of 2.1. In other words, the preferred range for b1 is 0.5 to 6.0, more preferably 0.8 to 4.0, more preferably 1.1 to 3.0, more preferably 1.4 to 3.0, more preferably 1.8 to 2.5, and particularly preferably 1.9 to 2.1. The preferred lower limits for c1 are, in order of preference, 0.2, 0.3, 0.4, 0.5, and 0.6, with a particularly preferred value of 0.7. The preferred upper limits are, in order of preference, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, and 1.0, with a particularly preferred value of 0.9. In other words, the preferred range for c1 is 0.2 to 8.0, more preferably 0.2 to 7.0, more preferably 0.2 to 6.0, more preferably 0.2 to 5.0, more preferably 0.3 to 4.0, more preferably 0.4 to 3.0, more preferably 0.5 to 2.0, more preferably 0.6 to 1.0, with a particularly preferred range of 0.7 to 0.9. The preferred lower limits for d1 are, in order of preference, 1.0, 3.0, 4.0, 5.0, 6.0, 6.5, and 7.0, with a particularly preferred value of 7.2. The preferred upper limits are, in order of preference, 9.5, 9.0, 8.5, and 8.0, with a particularly preferred value of 7.6. That is, the preferred range for d1 is 1.0 to 9.5, more preferably 3.0 to 9.5, more preferably 4.0 to 9.0, more preferably 5.0 to 9.0, more preferably 6.0 to 8.5, more preferably 6.5 to 8.5, more preferably 7.0 to 8.0, with a particularly preferred range of 7.2 to 7.6. Furthermore, there is a preferred range for c1+d1, with the lower limit being, in order of preference, 0, 2.0, 4.0, 6.0, 7.0, and 7.5, and particularly preferred being 8.0. The upper limit being, in order of preference, 20.0, 15.0, 12.5, 11.0, 10.0, and 9.0, and particularly preferred being 8.5. In other words, the preferred range for c1+d1 is 0 to 20.0, more preferably 2.0 to 15.0, more preferably 4.0 to 12.5, more preferably 6.0 to 11.0, more preferably 7.0 to 10.0, more preferably 7.0 to 9.0, more preferably 7.5 to 9.0, and particularly preferred being 8.0 to 8.5. The preferred lower limit of e1 is 0.1, 0.2, 0.5, 0.6, 0.8, and 1.0, with a particularly preferred value of 1.1. The preferred upper limit is 1.7, 1.6, 1.5, and 1.4, with a particularly preferred value of 1.3. In other words, the preferred range for e1 is 0.1 to 1.7, more preferably 0.2 to 1.6, more preferably 0.5 to 1.5, more preferably 0.6 to 1.4, more preferably 0.8 to 1.4, more preferably 1.0 to 1.4, and particularly preferably 1.1 to 1.3. The lower limit of f1 is preferably 0.05, 0.1, and 0.2, with a particularly preferred value of 0.3. The upper limit is preferably 1.8, 1.5, 1.0, 0.8, and 0.6, with a particularly preferred value of 0.5. In other words, the preferred range for f1 is 0.05 to 1.8, more preferably 0.1 to 1.5, more preferably 0.2 to 1.0, more preferably 0.2 to 0.8, more preferably 0.2 to 0.6, and particularly preferably 0.3 to 0.5. The preferred upper limits for g1 are, in order of preference, 1.8, 1.5, 1.0, 0.8, and 0.5, and the preferred lower limit is 0. That is, the preferred range for g1 is 0 or more and 1.8 or less, more preferably 0 or more and 1.5 or less, more preferably 0 or more and 1.0 or less, 0 or more and 0.8 or less, 0 or more and 0.5 or less, and particularly preferably 0 or more and 0.2 or less. The preferred lower limits for h1 are, in order of preference, 0.05, 0.10, and 0.12, with a particularly preferred value of 0.15. The preferred upper limits are, in order of preference, 2.50, 2.00, 1.50, 1.00, 0.80, 0.50, and 0.30, with a particularly preferred value of 0.25. In other words, the preferred range for h1 is 0.05 to 2.50, more preferably 0.10 to 2.00, more preferably 0.12 to 1.50, more preferably 0.12 to 1.00, more preferably 0.12 to 0.80, more preferably 0.12 to 0.50, more preferably 0.12 to 0.30, with a particularly preferred range of 0.15 to 0.25. Potassium, cesium, and rubidium are preferred as Y, with cesium being the most preferred. The preferred upper limits for i1 are, in order of preference, 4.0, 3.0, 2.0, 1.8, 1.5, 1.0, 0.8, and 0.5, while the preferred lower limit is 0. That is, the more preferred range for i1 is 0 or greater and 0.5 or less, and particularly 0 or greater and 0.2 or less.

[0024] For the catalytically active components on the raw material gas outlet side, i.e., the second and subsequent k-th layers (2≦k≦n), a composition in which b1 to i1 are within the following ranges when a1=12 in the above formula (4) is preferred. The preferred lower limits for b1 are, in order of preference, 0.2, 0.5, 0.8, 1.1, 1.4, and 1.5, with a particularly preferred value of 1.6. The preferred upper limits are, in order of preference, 5, 4, 3, 2.6, and 2.3, with a particularly preferred value of 2. In other words, the preferred range for b1 is 0.2 to 5, more preferably 0.5 to 4, more preferably 0.8 to 3, more preferably 1.1 to 2.6, more preferably 1.4 to 2.6, more preferably 1.5 to 2.3, with a particularly preferred range of 1.6 to 2. The preferred lower limits for c1 are, in order of preference, 0.2, 0.4, 0.5, and 0.6, with a particularly preferred value of 0.7. The preferred upper limits are, in order of preference, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, and 1.0, with a particularly preferred value of 0.9. In other words, the preferred range for c1 is 0.2 to 8, more preferably 0.2 to 7, more preferably 0.2 to 6, more preferably 0.2 to 5, more preferably 0.4 to 4, more preferably 0.5 to 3, more preferably 0.6 to 2, more preferably 0.7 to 2, with a particularly preferred range of 0.7 to 0.9. The preferred lower limits for d1 are, in order of preference, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, and 6.5, with a particularly preferred value of 7.0. The preferred upper limits are, in order of preference, 9.5, 9.0, and 8.5, with a particularly preferred value of 8.0. That is, the preferred range for d1 is 1.0 to 9.5, more preferably 2.0 to 9.5, more preferably 3.0 to 9.5, more preferably 4.0 to 9.5, more preferably 5.0 to 9.5, more preferably 6.0 to 9.0, more preferably 6.5 to 8.5, and a particularly preferred range of 7.0 to 8.0. Furthermore, there is a preferred range for c1+d1, with the lower limit being, in order of preference, 0, 2.0, 4.0, 6.0, 7.0, and 7.5, and particularly preferred being 7.8. The upper limit being, in order of preference, 20.0, 15.0, 12.5, 11.0, 10.0, and 9.0, and particularly preferred being 8.8. In other words, the preferred range for c1+d1 is 0 to 20.0, more preferably 2.0 to 15.0, more preferably 4.0 to 12.5, more preferably 6.0 to 11.0, more preferably 7.0 to 10.0, more preferably 7.5 to 9.0, and particularly preferred being 7.7 to 8.9. The preferred lower limits for e1 are 0.5, 1.0, 1.3, 1.4, and 1.5, with a particularly preferred value of 1.6. The preferred upper limits are 4.0, 3.0, 2.5, 2.0, and 1.9, with a particularly preferred value of 1.8. In other words, the preferred range for e1 is 0.5 to 4.0, more preferably 1.0 to 3.0, more preferably 1.3 to 2.5, more preferably 1.4 to 2.0, more preferably 1.5 to 1.9, and particularly preferably 1.60 to 1.80. The preferred lower limits for f1 are, in order of preference, 1.8, 1.5, 1.0, 0.8, and 0.5, with 0 being the preferred lower limit. That is, the preferred range for f1 is 0 to 1.8, more preferably 0 to 1.5, more preferably 0 to 1.0, more preferably 0 to 0.8, more preferably 0 to 0.5, and particularly preferably 0 to 0.2. The preferred upper limits for g1 are, in order of preference, 1.8, 1.5, 1.0, 0.8, and 0.5, and the preferred lower limit is 0. That is, the preferred range for g1 is 0 or more and 1.8 or less, more preferably 0 or more and 1.5 or less, more preferably 0 or more and 1.0 or less, more preferably 0 or more and 0.8 or less, more preferably 0 or more and 0.5 or less, and particularly preferably 0 or more and 0.2 or less. The preferred lower limits for h1 are, in order of preference, 0.05, 0.07, and 0.08, with a particularly preferred value of 0.09. The preferred upper limits are, in order of preference, 2.0, 1.5, 1.0, 0.8, 0.5, 0.3, and 0.2, with a particularly preferred value of 0.15. In other words, the preferred range for h1 is 0.05 to 2.0, more preferably 0.07 to 1.5, more preferably 0.08 to 1.0, more preferably 0.05 to 0.8, more preferably 0.07 to 0.5, more preferably 0.08 to 0.5, more preferably 0.08 to 0.3, with a particularly preferred range of 0.09 to 0.15. Potassium, cesium, and rubidium are preferred as Y, with cesium being the most preferred. The preferred upper limits for i1 are, in order of preference, 4.0, 3.0, 2.0, 1.8, 1.5, 1.0, 0.8, and 0.5, and the preferred lower limit is 0. That is, the preferred range for i1 is 0 to 4.0, more preferably 0 to 3.0, more preferably 0 to 2.0, more preferably 0 to 1.8, more preferably 0 to 1.5, more preferably 0 to 1.0, more preferably 0 to 0.8, more preferably 0 to 0.5, and particularly preferably 0 to 0.2.

[0025] [Carbohydrate coverage rate] The catalyst used in the present invention is preferably a spherical catalyst supported on an inert carrier. As the material for the inert support, known materials such as alumina, silica, titania, zirconia, niobia, silica-alumina, silicon carbide, carbides, steatite, and mixtures thereof can be used, but silica and / or alumina are preferred, and a mixture of silica and alumina is particularly preferred. When the catalyst used in this invention is a supported catalyst, it is preferable that the support ratio is 25% or more. This support ratio is calculated using the following formula. The mixing ratio of the inert carrier and the pre-calcined powder depends on the weight of each raw material. Loading rate (mass %) = (mass of pre-calcined powder used for molding) / {(mass of pre-calcined powder used for molding) + (mass of carrier used for molding)} × 100 More preferable lower limits for the loading rate are 25%, 28%, 30%, 32%, and 34%, with a particularly preferred rate of 35%. Similarly, preferred upper limits are 70%, 60%, 58%, 57%, and 56%, with a particularly preferred rate of 55%. Therefore, the preferred range is 25% to 70%, more preferably 28% to 60%, more preferably 30% to 58%, more preferably 32% to 57%, more preferably 34% to 56%, and particularly preferably 35% to 55%. Furthermore, it is preferable to use a binder when loading the material. Specific examples of binders that can be used include water, ethanol, methanol, propanol, polyhydric alcohols, polymeric binders such as polyvinyl alcohol, and inorganic binders such as silica sol aqueous solutions. However, ethanol, methanol, propanol, and polyhydric alcohols are preferred, as are diols such as ethylene glycol and triols such as glycerin. An aqueous solution of glycerin with a concentration of 5% to 50% by mass is preferred. By using an appropriate amount of aqueous glycerin solution, good moldability is achieved, and a high-performance catalyst with high mechanical strength can be obtained. The amount of binder used is usually 1 to 60 parts by mass per 100 parts by mass of pre-calcined powder, but in the case of aqueous glycerin solution, 5 to 30 parts by mass is preferred. When loading, the binder and pre-calcined powder may be supplied to the molding machine alternately or simultaneously.

[0026] [Regarding methods for manufacturing catalysts, etc.] The starting materials for catalyst precursors and the elements constituting the catalyst are not particularly limited, but for example, as a starting material for the molybdenum component, molybdenum oxides such as molybdenum trioxide, molybdic acid or its salts such as molybdic acid, ammonium paramolybdate, ammonium metamolybdate, and molybdenum-containing heteropoly acids or their salts such as phosphomolybdic acid and silicomolybdic acid can be used.

[0027] As raw materials for the bismuth component, bismuth salts such as bismuth nitrate, bismuth carbonate, bismuth sulfate, and bismuth acetate, as well as bismuth trioxide and metallic bismuth, can be used. These raw materials can be used in solid form, as aqueous solutions, as nitric acid solutions, or as slurries of bismuth compounds obtained from these aqueous solutions, but it is preferable to use nitrates, their solutions, or slurries obtained from these solutions.

[0028] The raw materials for component Y in the above general formula (4) are not limited to those listed above, but include hydroxides, chlorides, carbonates, sulfates, nitrates, oxides, or acetates of the constituent elements (sodium, potassium, rubidium, cesium, thallium). Preferably, the compounds contain cesium, such as cesium hydroxide, cesium chloride, cesium carbonate, cesium sulfate, and cesium oxide, but cesium nitrate is particularly preferred. Component Y is mainly an alkali metal. Although thallium is not an alkali metal, it has properties similar to alkali metals, so it is included in component Y in this invention. In the following description, component Y, including thallium, may be simply referred to as "alkali metal".

[0029] As starting materials for other constituent elements, a combination of ammonium salts, nitrates, nitrites, carbonates, subcarbonates, acetates, chlorides, inorganic acids, salts of inorganic acids, heteropoly acids, salts of heteropoly acids, sulfates, hydroxides, organic acid salts, oxides, or mixtures thereof of metal elements commonly used in this type of catalyst may be used, but ammonium salts and nitrates are preferably used.

[0030] These catalytically active compounds may be used individually or in mixtures of two or more. Slurries can be obtained by uniformly mixing each active compound with water. There are no particular restrictions on the amount of water used in the slurry, as long as it is enough to completely dissolve or uniformly mix all the compounds used. The amount of water used should be determined appropriately considering the drying method and conditions. Typically, the amount of water is between 200 and 2000 parts by mass per 100 parts by mass of the total mass of the compounds used to prepare the slurry. While a large amount of water is acceptable, too much water increases the energy cost of the drying process and may also result in incomplete drying, among other disadvantages. Furthermore, the nitrate ion concentration in the slurry immediately before final drying is 8.0% by mass or more and 50% by mass or less, preferably 9.0% by mass or more and 45% by mass or less, more preferably 10.0% by mass or more and 40% by mass or less, and most preferably 11.0% by mass or more and 30% by mass or less. Similarly, the ammonium ion concentration in the slurry immediately before drying is 1.0% by mass or more and 10% by mass or less, preferably 1.2% by mass or more and 8% by mass or less, more preferably 1.5% by mass or more and 6% by mass or less, and most preferably 1.7% by mass or more and 4% by mass or less.

[0031] The slurry of the source compounds for each of the above component elements is preferably prepared by (a) mixing the above source compounds all at once, (b) mixing them all at once and then aging them, (c) mixing them in stages, (d) repeating the mixing and aging process in stages, and a combination of (a) to (d). Here, aging refers to "an operation in which industrial raw materials or semi-finished products are treated under specific conditions such as a certain time and a certain temperature to acquire or improve the required physical and chemical properties or to allow a predetermined reaction to proceed." In this invention, the certain time refers to a range of 5 minutes to 24 hours, and the certain temperature refers to a range of room temperature or higher and below the boiling point of an aqueous solution or aqueous dispersion. Of these, the method preferred in terms of the activity and yield of the final catalyst is (c) the method of mixing in stages, more preferably the method in which each raw material to be mixed in the mother liquor in stages is a fully dissolved solution, and most preferably the method in which a mother liquor made from a molybdenum raw material is mixed with various mixtures of alkali metal solutions and nitrates.

[0032] In this invention, there are no particular restrictions on the shape of the stirring blades used when mixing the essential active ingredients. Any stirring blades such as propeller blades, turbine blades, paddle blades, inclined paddle blades, screw blades, anchor blades, ribbon blades, and large grid blades can be used in one stage or in two or more stages of the same blade or different blades in the vertical direction. In addition, baffles may be installed in the reaction vessel as needed.

[0033] Next, the slurry obtained in this way is dried. The drying method is not particularly limited as long as it can completely dry the slurry, but examples include drum drying, freeze-drying, spray drying, and evaporation to dryness. Of these, spray drying, which can dry the slurry into powder or granules in a short time, is particularly preferred in the present invention. The drying conditions for spray drying vary depending on the slurry concentration, liquid delivery rate, etc., but generally the temperature at the outlet of the dryer is between 70°C and 150°C.

[0034] The catalyst precursor obtained as described above can be molded and then fired to control and maintain its molded shape, resulting in a catalyst with particularly excellent mechanical strength for industrial applications and stable catalytic performance. A pre-firing step may be performed before molding if necessary.

[0035] The molding process can employ either supported molding, where the catalyst is supported on a carrier such as silica, or unsupported molding, where no carrier is used. Specific molding methods include, for example, tableting, press molding, extrusion molding, and granulation molding. The shape of the molded product can be appropriately selected from cylindrical, ring-shaped, spherical, etc., depending on the operating conditions. However, a supported catalyst is used, in which the catalytically active component is supported on a spherical carrier, particularly an inert carrier such as silica or alumina, with an average particle size of 1.0 mm to 10.0 mm, preferably 1.0 mm to 8.0 mm. In addition, small amounts of known additives, such as graphite or talc, may be added during molding. It should be noted that molding aids, pore-forming agents, and carriers added during molding are not considered as constituent elements of the active component in this invention, regardless of whether they are active in the sense of converting the raw material into some other product.

[0036] The pre-calcination method (calcination of the catalyst precursor before molding) and pre-calcination conditions, or the main calcination method (calcination after molding) and main calcination conditions are not particularly limited, and known processing methods and conditions can be applied. The optimal conditions for pre-calcination and main calcination vary depending on the catalyst raw materials used, catalyst composition, preparation method, etc., but are usually carried out under the flow of an oxygen-containing gas such as air or an inert gas at a temperature of 200°C to 600°C, preferably 300°C to 550°C, for 0.5 hours or more, preferably 1 hour to 40 hours. Here, an inert gas refers to a gas that does not reduce the reaction activity of the catalyst, and specifically, examples include nitrogen, carbon dioxide, helium, argon, etc. In particular, main calcination is an important step in determining the activity of the catalyst in the present invention, but when the activity of the catalyst is low or high, it is known to those skilled in the art that the activity can be adjusted by changing the process parameters of the main calcination step, i.e., the oxygen content in the atmosphere, the maximum temperature reached, the calcination time, etc., to obtain the highest yield of the composition, and this falls within the scope of the present invention. Furthermore, the main firing process shall be carried out after the aforementioned pre-firing process, and the maximum temperature reached in the main firing process (main firing temperature) shall be higher than the maximum temperature reached in the aforementioned pre-firing process (pre-firing temperature). In the catalyst manufacturing method used in the present invention, the upper limit of the main firing temperature is preferably 540°C or lower, more preferably 530°C or lower, and particularly preferably 520°C or lower. Furthermore, the lower limit of the main firing temperature is preferably 480°C or higher, and more preferably 490°C or higher. In this specification, the catalytic active component before molding after pre-calcination will be referred to as pre-calcined powder.

[0037] The above catalyst is preferably used as a catalyst for producing methacrolein and methacrylic acid compounds, and is even more preferably used as a catalyst in the first stage, i.e., for producing methacrolein.

[0038] <Catalyst particle size> The catalyst particle size used in the present invention is preferably 4.1 mm or more and 5.0 mm or less. More preferably, the upper limits are 4.9 mm, 4.8 mm, 4.7 mm, and 4.6 mm, in that order, with 4.5 mm being particularly preferred. The lower limits are preferably 4.2 mm and 4.3 mm, in that order. That is, the most preferred range is 4.3 mm or more and 4.5 mm or less. The catalyst particle size is the number average of the triaxial average diameters, which are calculated from the average of the catalyst's length (L), width (B), and thickness (T). The triaxial average diameter is derived using the following formula (C). [Number C] Triaxial average diameter (mm) = (L+B+T) / 3 (C) In the case of spherical catalysts, the length (L), width (B), and thickness (T) of the catalyst used in calculating the triaxial average diameter are determined by measuring the diameters of three axes that pass through the centroid of the sample and are orthogonal to each other, and listing them in descending order of size. The measurement can be performed on a randomly sampled portion of the catalyst, but for example, it should be performed on 300 or more catalyst particles and represent the arithmetic mean.

[0039] <Regarding the second stage catalyst> When the above catalyst is used as a catalyst for producing methacrolein, methacrylic acid can be obtained by carrying out a second oxidation reaction with methacrolein. In this case, the catalyst represented by the following formula (5) is preferred as the second stage catalyst. Mo 10 V a2 P b2 Cu c2 Cs d2 (NH4) e2 X f2 O g2 (5) In the formula, Mo represents molybdenum, V represents vanadium, P represents phosphorus, Cu represents copper, Cs represents cesium, (NH4) represents an ammonium group, and X represents one or more elements selected from the group consisting of Sb, As, Ag, Mg, Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, Th, K, and Rb. a2 to g2 represent the atomic ratios of each element, satisfying the following: a2 = 0.1 ≤ a2 ≤ 6.0, b2 = 0.5 ≤ b2 ≤ 6.0, c2 = 0 ≤ c2 ≤ 3.0, d2 = 0 ≤ d2 ≤ 3.0, e2 = 0 ≤ e2 ≤ 3.0, and f2 = 0 ≤ f2 ≤ 3.0. g2 is a value determined by the valence of each element.

[0040] According to the above catalyst, in reactions to produce the corresponding methacrolein and methacrylic acid using isobutylene, t-butyl alcohol, etc. as raw materials, particularly in reactions to produce methacrolein and methacrylic acid by gas-phase catalytic oxidation of isobutylene and t-butyl alcohol with molecular oxygen or a molecular oxygen-containing gas, the target product can be produced in high yield.

[0041] The catalyst thus obtained is used to produce methacrolein and / or methacrylic acid by gas-phase catalytic oxidation of at least one raw material selected from, for example, isobutylene and t-butyl alcohol, using a molecular oxygen-containing gas, and is particularly effective in producing methacrolein and / or methacrylic acid. In the production method of the present invention, the method of supplying the raw material gas may be a normal single-flow method or a recycling method, and can be carried out under generally used conditions and is not particularly limited. For example, a mixed gas consisting of isobutylene as a starting material at room temperature in an amount of 1 to 10 vol%, preferably 4 to 9 vol%, more preferably 4 to 7.5 vol%, most preferably 5 to 7 vol%, molecular oxygen in an amount of 3 to 20 vol%, preferably 4 to 18 vol%, water vapor in an amount of 0 to 60 vol%, and an inert gas such as carbon dioxide or nitrogen in an amount of 20 to 80 vol%, preferably 30 to 60 vol%, is filled into a reaction tube and carried out on a catalyst at 250 to 450°C, under a pressure of normal pressure to 10 atm, with a space velocity of 300 to 5000 h -1 It is introduced and the reaction is carried out. [Examples]

[0042] The present invention will be described in more detail below with reference to examples. In the examples, the raw material conversion rate, effective yield, and loading rate were calculated according to the following formulas. Raw material conversion rate (%) = (moles of t-butyl alcohol or isobutylene reacted) / (moles of t-butyl alcohol or isobutylene supplied) × 100 Effective yield (%) = (Total number of moles of methacrolein and methacrylic acid produced) / (Number of moles of t-butyl alcohol or isobutylene supplied) × 100 Loading rate (mass %) = (mass of pre-calcined powder used for molding) / {(mass of pre-calcined powder used for molding) + (mass of carrier used for molding)} × 100

[0043] (Preparation of Catalyst 1) The composition ratio of the catalytically active component excluding oxygen is in atomic ratio Mo 12 Bi 2.2 Ni 0.7 Co 7.3 Fe 1.2 Ce 0.4 Cs 0.2 Using the required amount of raw materials, the catalyst was manufactured according to the following procedure. Aqueous solution (A) was obtained by dissolving ammonium molybdate and cesium nitrate in distilled water while heating and stirring. Separately, aqueous solution (B) was prepared by dissolving cobalt nitrate, nickel nitrate, ferric nitrate, and cerium nitrate in distilled water, and aqueous solution (C) was prepared by dissolving bismuth nitrate in distilled water that had been acidified by adding concentrated nitric acid. Aqueous solutions (B) and (C) were sequentially mixed into aqueous solution (A) with vigorous stirring, and the resulting suspension was dried using a spray dryer. The resulting powder was calcined at 440°C for 4 hours to obtain pre-calcined powder (D). The pre-calcined powder (D) was then supported on an inert carrier (alumina, particle size 4.0 mm) using a rolling granulator at a ratio of 40% by mass relative to the molded catalyst. Crystalline cellulose was added at 5% by mass to the pre-calcined powder (D) as a strength improver. The molded product thus obtained was calcined at 515°C for 5 hours to obtain catalyst 1. The particle size of catalyst 1 was 4.5 mm.

[0044] (Preparation of Catalyst 2) The composition ratio of the catalytically active component excluding oxygen is in atomic ratio Mo 12 Bi 1.7 Ni 0.8 Co 7.2 Fe 1.8 Cs 0.1 Using the required amount of raw materials, the catalyst was manufactured according to the following procedure. Aqueous solution (E) was prepared by dissolving ammonium molybdate and cesium nitrate in distilled water while heating and stirring. Separately, aqueous solution (F) was prepared by dissolving cobalt nitrate, nickel nitrate, and ferric nitrate in distilled water, and aqueous solution (G) was prepared by dissolving bismuth nitrate in distilled water that had been acidified by adding concentrated nitric acid. Aqueous solutions (F) and (G) were sequentially mixed into aqueous solution (E) with vigorous stirring, and the resulting suspension was dried using a spray dryer. The resulting powder was calcined at 440°C for 4 hours to obtain pre-calcined powder (H). The pre-calcined powder (H) was then supported on an inert carrier (alumina, particle size 4.0 mm) using a rolling granulator at a ratio of 40% by mass relative to the molded catalyst. Crystalline cellulose was added at 5% by mass to the pre-calcined powder (H) as a strength improver. The molded product thus obtained was calcined at 510°C for 5 hours to obtain catalyst 2. The particle size of catalyst 2 was 4.4 mm.

[0045] (Production of methacrolein and methacrylic acid) The catalyst obtained by the above preparation method was evaluated for its reaction using the following method. A stainless steel reaction tube with an inner diameter of 28 mm was filled with a total of 47.0 mL of catalyst, including an inert substance for dilution. A gas mixture with a volume ratio of isobutylene:oxygen:nitrogen:water vapor = 1:2.0:11.9:1.6 was used, under an outlet pressure of 50 kPaG, and with a GHSV (Gas Hourly Space Velocity) of 1052 hr. -1Under these conditions, the reaction was carried out at a reaction bath temperature of 350°C for more than 50 hours. After the reaction, the condensate and gas components were separated at the outlet of the reaction tube using a condenser, and each component in the gas and condensate was quantitatively analyzed using a gas chromatograph equipped with a flame ionization detector and a heat conduction detector, respectively. The data obtained from the gas chromatograph were factor-corrected to calculate the raw material conversion rate and effective yield. Subsequently, after more than 1000 hours of reaction while adjusting the reaction bath temperature to maintain an isobutylene conversion rate of 99.0% or higher, quantitative analysis was performed again.

[0046] [Example 1] The catalyst layers were arranged sequentially from the raw material gas inlet side of the reaction tube toward the raw material gas outlet, as follows: Catalyst 1 was packed to 38% of the total packing length as the first catalyst layer (raw material gas inlet side), and catalyst 2 was packed to 62% of the total packing length as the second catalyst layer, resulting in a two-layer catalyst structure. The resulting catalyst layers A1-A2 and their evaluation results are shown in Table 1.

[0047] [Comparative Example 1] Catalyst 1 was packed to 100% of its total length, forming a single catalyst layer. The resulting catalyst layers A1-A2 and their evaluation results are shown in Table 1.

[0048] [Comparative Example 2] Catalyst 2 was filled to 100% of its total length, resulting in a single-layer catalyst structure. The resulting catalyst layers A1-A2 and their evaluation results are shown in Table 1.

[0049] [Table 1]

[0050] Table 1 shows the reaction bath temperature and effective yield at the initial and final stages of the reaction for the examples and comparative examples. As is clear from Table 1, the present invention allows for obtaining the target product at a low reaction bath temperature while maintaining a high effective yield.

[0051] (Preparation of catalyst 3) The composition ratio of the catalytically active component excluding oxygen is in atomic ratio Mo 12Bi 2.2 Ni 0.4 Co 7.2 Fe 1.2 Ce 0.4 Cs 0.2 Using raw materials in amounts to achieve the above, production was carried out in the same procedure as for Catalyst 1 to obtain Catalyst 3. The particle size of Catalyst 3 was 4.5 mm.

[0052] (Preparation of Catalyst 4) The composition ratio of the catalytically active components excluding oxygen, in atomic ratio, is Mo 12 Bi 2.0 Ni 0.8 Co 7.4 Fe 1.5 Ce 0.2 Cs 0.2 Using raw materials in amounts to achieve the above, production was carried out in the same procedure as for Catalyst 1 to obtain Catalyst 4. The particle size of Catalyst 4 was 4.5 mm.

[0053] (Preparation of Catalyst 5) The composition ratio of the catalytically active components excluding oxygen, in atomic ratio, is Mo 12 Bi 2.6 Ni 1.3 Co 5.2 Fe 1.0 Ce 1.2 Cs 0.2 Using raw materials in amounts to achieve the above, production was carried out in the same procedure as for Catalyst 1 to obtain Catalyst 5. The particle size of Catalyst 5 was 4.5 mm.

[0054] [Example 2] A catalyst layer was provided sequentially from the raw material gas inlet side of the reaction tube toward the raw material gas outlet as follows. As the first catalyst layer (on the raw material gas inlet side), Catalyst 3 was packed to 38% of the total packing length, and as the second catalyst layer, Catalyst 2 was packed to 62% of the total packing length, forming a two-layer structure of the catalyst layer. A1-A2 of the catalyst layer thus formed and the evaluation results are shown in Table 2.

[0055] [Example 3] The catalyst layers were arranged sequentially from the raw material gas inlet side of the reaction tube toward the raw material gas outlet, as follows: Catalyst 4 was packed to 38% of the total packing length as the first catalyst layer (raw material gas inlet side), and catalyst 2 was packed to 62% of the total packing length as the second catalyst layer, resulting in a two-layer catalyst structure. The resulting catalyst layers A1-A2 and their evaluation results are shown in Table 2.

[0056] [Example 4] The catalyst layers were arranged sequentially from the raw material gas inlet side of the reaction tube toward the raw material gas outlet, as follows: Catalyst 5 was packed to 38% of the total packing length as the first catalyst layer (raw material gas inlet side), and catalyst 2 was packed to 62% of the total packing length as the second catalyst layer, resulting in a two-layer catalyst structure. The resulting catalyst layers A1-A2 and their evaluation results are shown in Table 2.

[0057] [Comparative Example 3] The catalyst layers were arranged sequentially from the raw material gas inlet side of the reaction tube toward the raw material gas outlet, as follows: Catalyst 2 was packed to 38% of the total packing length as the first catalyst layer (raw material gas inlet side), and Catalyst 1 was packed to 62% of the total packing length as the second catalyst layer, resulting in a two-layer catalyst structure. The resulting catalyst layers A1-A2 and their evaluation results are shown in Table 2.

[0058] [Table 2]

[0059] Table 2 shows the reaction bath temperature and effective yield at the initial and final stages of the reaction for the examples and comparative examples. As is clear from Table 2, the present invention allows for the acquisition of the target product at a low reaction bath temperature while maintaining a high effective yield. [Industrial applicability]

[0060] By using the production method of the present invention, it is possible to obtain high yields even in regions with high raw material conversion rates when oxidatively producing unsaturated aldehyde compounds and unsaturated carboxylic acid compounds. Furthermore, by using the production method of the present invention, as the yield improves, a reduction in by-products that cause reactor clogging is expected, enabling stable and low-cost operation of the gas-phase catalytic oxidation method.

Claims

1. A method for producing an unsaturated aldehyde compound or an unsaturated carboxylic acid compound using a fixed-bed multitubular reactor having multiple reaction tubes, The reaction tube is provided with two or more catalyst layers in the direction of gas flow. The atomic ratio A of cerium to molybdenum in the catalytically active component of the catalyst packed in the first layer from the raw material gas inlet. １ and, The atomic ratio A of cerium to molybdenum in the catalytically active component of the catalyst packed in the k-th layer, which is one of the layers from the second layer onwards from the raw material gas inlet. ｋ And satisfy the relationship in equation (1) below. A 1 -A ｋ >0 (1) A method for producing unsaturated aldehyde compounds or unsaturated carboxylic acid compounds.

2. The atomic ratio B of iron to molybdenum in the catalytically active component of the catalyst packed in the first layer from the raw material gas inlet. 1 and, The atomic ratio B of iron to molybdenum in the catalytically active component of the catalyst packed into the k layer ｋ And satisfy the relationship in equation (2) below. B ｋ -B １ >0 (2) The manufacturing method according to claim 1.

3. Atomic ratio A of cerium element to molybdenum element contained in the catalytically active component of the catalyst packed in the first layer from the raw material gas inlet part １ and atomic ratio B of iron element １ the sum of (A １ + B １ ), and The atomic ratio A of cerium element to molybdenum element in the catalytically active component of the catalyst packed in the k layer ｋ and the atomic ratio of iron element B ｋ The sum of (A ｋ +B ｋ ) and satisfy the following equation (3). (A ｋ +B ｋ )-(A １ +B １ )>0 (3) The manufacturing method according to claim 1 or 2.

4. The manufacturing method according to claim 1, wherein the catalyst packed in the first layer from the raw material gas inlet has a catalytically active component having a composition represented by the following formula (4). Mo ａ１ Bi ｂ１ Ni ｃ１ Co ｄ１ Fe ｅ１ Ce f１ X g１ Y h１ Z ｉ１ O ｊ１ ・・・(4) In the formula, Mo, Bi, Ni, Co, Fe, and Ce represent molybdenum, bismuth, nickel, cobalt, iron, and cerium, respectively; X is at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, and titanium; Y is at least one element selected from sodium, potassium, cesium, rubidium, and thallium; and Z is an element belonging to groups 1 through 16 of the periodic table, selected from elements other than Mo, Bi, Ni, Co, Fe, Ce, X, and Y. This refers to at least one element, where a1, b1, c1, d1, e1, f1, g1, h1, i1, and j1 represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, cerium, X, Y, Z, and oxygen, respectively. When a1 = 12, the following inequalities hold: 1.5 < b1 ≤ 7.0, 0 ≤ c1 ≤ 10.0, 0 ≤ d1 ≤ 8.0, 0.0 ≤ c1 + d1 ≤ 17.0, 0 < e1 ≤ 1.8, 0 < f1 ≤ 2.0, 0 ≤ g1 ≤ 3.0, 0 ≤ h1 ≤ 5.0, and 0 ≤ i1 ≤ 5.

0. j1 is a value determined by the oxidation state of each element.

5. The manufacturing method according to claim 4, wherein the catalyst packed in the first layer from the raw material gas inlet has a catalytic active component having a composition in formula (4) above where a1 = 12, the range of b1 is 1.8 ≤ b1 ≤ 2.4, the range of c1 is 0.3 ≤ c1 ≤ 1.6, the range of d1 is 4.8 ≤ d1 ≤ 8.0, the range of c1 + d1 is 5.2 ≤ c1 + d1 ≤ 9.5, the range of e1 is 0.8 ≤ e1 ≤ 1.2, the range of f1 is 0.3 ≤ f1 ≤ 1.6, g1 is 0, the range of h1 is 0.12 ≤ h1 ≤ 0.25, and i1 is 0.

6. The manufacturing method according to claim 1 or 4, wherein the loading rate of the catalyst packed in the first layer from the raw material gas inlet is 35% or more and 55% or less.

7. The manufacturing method according to claim 1 or 4, wherein the particle size of the catalyst packed in the first layer from the raw material gas inlet is 4.1 mm or more and 5.0 mm or less.

8. The production method according to claim 1 or 4, wherein the unsaturated aldehyde compound is methacrolein and the unsaturated carboxylic acid compound is methacrylic acid.

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