Method for producing unsaturated aldehyde and / or unsaturated carboxylic acid

Abstract

To provide a method for producing an unsaturated aldehyde or an unsaturated carboxylic acid, comprising subjecting propylene, isobutylene, t-butyl alcohol or the like as a raw material to gas-phase catalytic oxidation to produce the corresponding unsaturated aldehyde or unsaturated carboxylic acid, by which the objective product can be produced in a high yield even in a region having a high raw material conversion.SOLUTION: A method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid using a fixed-bed multitubular reactor, comprising providing a plurality of catalyst layers formed by dividing a reaction tube into n pieces (n is 2 or more) in the gas flow direction, wherein a ratio (A1 / A2) of a catalyst activity component density (A1) from a raw material gas inlet portion to a half of a total filling length to a catalyst activity component density (A2) from the half of the total filling length to a raw material gas outlet portion is 1.10 to 2.00.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a production method that enables stable, high-yield production even in the range of high raw material conversion rates when producing unsaturated aldehydes or unsaturated carboxylic acids by oxidative method. [Background technology]

[0002] Methods for producing corresponding unsaturated aldehydes and unsaturated carboxylic acids using raw materials such as propylene, isobutylene, and t-butyl alcohol are widely used industrially, and many reports have been published on means for improving the yield of these production methods (e.g., Patent Documents 1 and 2).

[0003] Despite the above-mentioned improvements, further yield improvements are needed in the production of corresponding unsaturated aldehydes and / or unsaturated carboxylic acids by partial oxidation of propylene, isobutylene, t-butyl alcohol, etc. For example, the yield of the target product determines the amount of propylene, isobutylene, t-butyl alcohol, etc. required for production, which significantly impacts production costs. Furthermore, continued operation at low yields generates large amounts of by-products, which places a heavy burden on the purification process, increasing the time required for the purification process and operating costs. Furthermore, depending on the type of by-product, they may accumulate on the catalyst surface or in the gas flow path near the catalyst. These by-products may cover necessary reactive sites on the catalyst surface, reducing the catalyst's activity, which forces an increase in activity and necessitates an increase in the reaction bath temperature. This results in thermal stress on the catalyst, shortening its lifespan and further reducing selectivity, leading to a decrease in yield. Furthermore, by-products accumulated in the system can cause an increase in the system pressure, which can lead to a decrease in selectivity and a decrease in yield, and in the worst case scenario, a sudden increase in internal pressure can cause an abnormal temperature and a runaway reaction, which can lead to a long-term shutdown of the system and the need to clean the system and replace the catalyst.

[0004] Furthermore, Patent Document 3 reports a method for improving yield by controlling the composition of the support used when molding the catalyst into a supported catalyst and the catalyst particle size after molding. It has been found that the method of using such catalysts characterized by their shape is also important. In particular, when using a catalyst with a generally small catalyst particle size, a high space velocity causes an increase in the pressure within the system, which reduces the selectivity and leads to a decrease in yield. Therefore, it is clear that further development of a catalyst packing method that can maximize the catalyst's performance is necessary.

[0005] In the production of unsaturated aldehydes and / or unsaturated carboxylic acids by partial oxidation of propylene, isobutylene, t-butyl alcohol, etc., localized areas of abnormally high temperature (hot spots) in the catalyst bed are considered a major problem. Many production methods have been reported that suppress heat accumulation at hot spots, improve yield, and extend catalyst life. To avoid the occurrence of such hot spots or heat accumulation at hot spots, measures such as accepting low productivity or reducing the diameter of the reaction tube have been taken, but these methods are undeniably economically disadvantageous. Therefore, various studies have been conducted and reported to avoid the dangers of reaction operation due to hot spots and ensure the economic viability of the industrial production. For example, methods such as diluting the catalyst at the hot spot with an inert substance (Patent Document 4) and reducing the amount of active component loaded on the catalyst at the hot spot (Patent Document 5) have been proposed. These methods commonly aim to avoid the occurrence of hot spots by reducing the amount of catalytic active component at the inlet of the reaction tube, where hot spots are more likely to occur. However, these methods increase the load on the catalyst because the amount of catalytically active components at the inlet of the reaction tube, where the reaction conversion rate is high, is reduced, and in some cases, the effects of improving the yield and extending the catalyst life are not achieved depending on the form of the catalyst used and the reaction conditions. Therefore, it is difficult to say that the means of suppressing the formation of hot spots by reducing the amount of catalytically active components at the inlet of the reaction tube is a sufficient method for improving the yield and extending the catalyst life. Therefore, there is a need for the development of a catalyst and a production method that can achieve the effects of improving the yield and extending the catalyst life without reducing the amount of catalytically active components, but by increasing it if possible.

[0006] On the other hand, gas-phase catalytic oxidation reactions using isobutylene or t-butyl alcohol as raw materials pose unique challenges, such as the generation of relatively high-boiling compounds such as maleic acid and terephthalic acid in addition to the main product methacrolein, and the inclusion of polymers and tar-like substances in the reaction product gas. If the reaction product gas containing such substances is directly subjected to the downstream reaction, these substances can cause blockages in the piping and downstream catalyst packed bed, resulting in increased pressure loss, reduced catalytic activity, and reduced selectivity to methacrylic acid. Furthermore, industrial production must be stopped to remove the blockages, resulting in a significant decrease in production. These problems frequently occur when the feed rate of isobutylene and / or t-butyl alcohol or the concentration of isobutylene and / or t-butyl alcohol is increased to increase methacrylic acid productivity.

[0007] Commonly adopted countermeasures to prevent such problems include periodically stopping the reaction and removing and replacing the inert material packed at the gas inlet side of the downstream catalyst to prevent clogging of the catalyst layer or a decrease in catalyst activity, or separating methacrolein from the upstream reaction product gas and then resupplying the separated methacrolein to the downstream reaction, thereby optimizing the oxidation reaction. Furthermore, methods have been proposed in which the raw material gas concentration is diluted more than necessary to reduce the by-product concentration. Patent Document 6 proposes a method of keeping the intermediate piping between the upstream and downstream reactions at a temperature above the boiling point of maleic anhydride to prevent clogging, or a method of devising a method of extremely high gas linear velocity. Patent Document 7 proposes a method of specifying the shape of the catalyst used in the downstream reaction to increase the void ratio between the catalyst and the catalyst to prevent clogging by solids from the upstream reactor. However, these methods are not fully satisfactory for industrial use, and the development of catalysts and production methods that can achieve further improvements in yield in order to reduce the amount of by-products produced is desired.

[0008] The direct oxidation process, which involves two-stage gas-phase catalytic oxidation reactions using isobutylene or t-butyl alcohol as raw materials to sequentially produce methacrolein and methacrylic acid, followed by esterification of methacrylic acid to produce methyl methacrylate, is expected to be a highly competitive process compared to other methyl methacrylate production processes because it is safer and less environmentally hazardous, utilizes reaction heat more efficiently, and reduces catalyst costs. In the first-stage reaction of this direct oxidation process, i.e., the reaction to produce methacrolein from isobutylene or t-butyl alcohol, unreacted isobutylene poisons the subsequent second-stage reaction. Therefore, it is necessary to increase the raw material conversion rate and minimize unreacted isobutylene. To increase raw material conversion, the reaction bath temperature is increased to increase isobutylene conversion. However, as noted in Non-Patent Document 1, it is generally known that the yield or selectivity of methacrolein and / or methacrylic acid drops sharply in the high isobutylene conversion range. That is, there is a need for the development of a production method that provides a high yield of methacrolein and / or methacrylic acid even in a high isobutylene conversion range.

[0009] To summarise, i) Avoiding hot spots and improving yield ii) Increasing the amount of catalytically active components and extending the catalyst life iii) When isobutylene or t-butyl alcohol is used as a raw material in a gas-phase catalytic oxidation reaction, the yield of methacrolein and / or methacrylic acid can be maintained at a high level even in a high isobutylene conversion range. This needs to be achieved, requiring significant technological innovation. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2016 / 136882 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-024009 [Patent Document 3] Japanese Patent Publication No. 2020-171906 [Patent Document 4] Japanese Patent Application Publication No. 47-010614 [Patent Document 5] Japanese Patent Application Publication No. 10-168003 [Patent Document 6] Japanese Patent Publication No. 50-126605 [Patent Document 7] Japanese Patent Application Publication No. 61-221149 [Non-patent literature]

[0011] [Non-Patent Document 1] Journal of Catalysis 236 No. 282-291 (2005) Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention proposes a vapor-phase catalytic oxidation method for producing the corresponding unsaturated aldehydes and unsaturated carboxylic acids using propylene, isobutylene, t-butyl alcohol, etc. as raw materials, which produces the target products in high yields even in the region where the raw material conversion rate is high. [Means for solving the problem]

[0013] The present inventors have conducted extensive research under these circumstances and have completed the present invention.

[0014] That is, the present invention relates to the following 1) to 13). 1) A method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid, which uses a fixed-bed multi-tubular reactor and has a plurality of catalyst layers formed by dividing the reactor into n sections (n ​​is 2 or more) in the gas flow direction of the reaction tube, A method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid, wherein the ratio (A1 / A2) of the density (A1) of the catalytic active component from the raw material gas inlet to half of the total filling length to the density (A2) of the catalytic active component from half of the total filling length to the raw material gas outlet is 1.10 to 2.0. 2) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to 1) above, wherein the ratio (R1 / R2) of the average catalyst particle diameter (R1) from the raw material gas inlet to the center of the total filling length to the average catalyst particle diameter (R2) from the center of the total filling length to the raw material gas outlet is 0.45 to 0.95. 3) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to 1) or 2) above, wherein a catalyst having a composition represented by the following formula (1) is used as the catalyst in the first layer of the reaction tube. [Formula 1] Mo i1 , h1 , , , Bi b1 Ni c1 Co d1 Fe e1 X f1 Y g1 Z <000000⑧> O i1 ···(1) (In the formula, Mo, Bi, Ni, Co, and Fe each represent molybdenum, bismuth, nickel, cobalt, and iron, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium, and titanium, Y represents at least one element selected from sodium, potassium, cesium, rubidium, and thallium, Z belongs to Group 1 to Group 16 of the periodic table and means at least one element selected from elements other than Mo, Bi, Ni, Co, Fe, X, and Y, and a1, b1, c1, d1, e1, f1, g1, h1, and i1 each represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, X, Y, Z, and oxygen. When a1 = 12, then 0 < b1 ≤ 7.0, 0 ≤ c1 ≤ 10.0, 0 ≤ d1 ≤ 10.0, 0 < e1 < 5.0, 0 ≤ f1 ≤ 2.0, 0 ≤ g1 ≤ 3.0, 0 ≤ h1 ≤ 5.0, and i1 is a value determined by the oxidation state of each element.) 4) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of the above 1) to 3), wherein a catalyst having an average catalyst particle diameter of 2.0 mm or more and 4.0 mm or less is used as the catalyst in the first layer of the reaction tube. 5) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to 3) or 4) above, wherein in the formula (1), 0 < e1 ≦ 1.7. 6) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of 3) to 5) above, wherein in the formula (1), 1.7 < b1 ≦ 7.0. 7) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of 3) to 6) above, wherein in the formula (1), 1.0 ≦ c1 ≦ 10.0. 8) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of 3) to 7) above, wherein in the formula (1), Y is cesium and 0.16 ≦ g1 ≦ 3.0. 9) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of 1) to 8) above, wherein A1 is 0.30 g / cm 3 or more and 1.0 g / cm 3 or less. 10) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of 1) to 9) above, wherein a catalyst supported on an inert carrier with a supported ratio exceeding 40% is used as the catalyst in the first layer of the reaction tube. 11) The method for producing an unsaturated aldehyde compound and / or an unsaturated carboxylic acid compound according to any one of 1) to 10) above, wherein the raw material conversion rate is 99.0% or more. 12) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of 1) to 11) above, wherein R1 is 2.0 mm or more and 4.49 mm or less. 13) 12) The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of 1) to 12) above, wherein the ratio (x1) of the packing length of the catalyst in the first layer to the total packing length is 10% or more and 90% or less. [Effects of the Invention]

[0015] The production method of the present invention is extremely effective in improving the yield in gas-phase catalytic oxidation reactions, and is useful when producing the corresponding unsaturated aldehydes and unsaturated carboxylic acids from raw materials such as propylene, isobutylene, and t-butyl alcohol. In particular, the method is effectively used in the production of corresponding unsaturated aldehydes using propylene, isobutylene, t-butyl alcohol, etc. as raw materials, particularly in the reaction of obtaining methacrolein by the vapor-phase catalytic oxidation of isobutylene. The use of the production method of the present invention in the vapor-phase catalytic oxidation reaction of isobutylene also contributes to improving the yield in the region where the raw material conversion rate is high. This is a particularly effective feature in the direct oxidation method, in which isobutylene becomes a poisonous substance in the subsequent reaction. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Catalyst layer] The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid of the present invention (hereinafter also referred to simply as the production method) is a production method in which a reaction tube in a fixed-bed multi-tube reactor is packed with a plurality of catalyst layers. In this specification, this state is expressed as "the catalyst layer is divided into n layers," where n represents 2 or more. In other words, this means that n catalyst layers are formed in the reaction tube. There is no particular limitation on n as long as it is 2 or more layers, and it can be appropriately set to about 10 layers taking into consideration the equipment conditions and the catalyst selection, but 2 or 3 layers are preferred, and 2 layers is more preferred. The catalysts in each layer differ from each other in one or more of the types of catalytically active components, the density of the catalytically active components, the average catalyst particle size, and the dilution rate with an inert carrier, which will be described below, but in the case of 3 or more layers, this does not exclude the case where the same catalyst is used in layers that are not adjacent to each other. In this specification, the catalyst layer is defined as the first layer from the raw material gas inlet, and the layer on the raw material gas outlet side is defined as the nth layer.

[0017] [Catalytic active component density ratio (A1 / A2)] The production method of the present invention is a method of packing so that the ratio (A1 / A2) of the catalytic active component density (A1) from the raw material gas inlet to half of the total packing length to the catalytic active component density (A2) from half of the total packing length to the raw material gas outlet is 1.1 to 2.0. In this specification, "~" includes the numbers before and after it. In the present invention, when the entire packing length from the inlet to the outlet of the catalyst in the longitudinal direction of the reaction tube is divided into two, the packing length region from the inlet to half of the entire packing length is referred to as the inlet side, and the packing length region from half of the entire packing length to the outlet is referred to as the outlet side, regardless of the number of catalyst layers. Note that the entire packing length is the length from the top to the bottom of the packed catalyst, and does not include an inlet inert (inert carrier) layer packed on the inlet side of the reaction tube for the purpose of residual heat, etc., or an outlet inert layer packed on the outlet side of the reaction tube for the purpose of heat dissipation, etc.

[0018] <Filling length ratio x m , y m , z m > To define A1 and A2, first, let the packing length ratio of the mth catalyst layer in the total packing length be x m , the ratio of the packing length of the mth catalyst layer to the packing length on the inlet side is y m , the ratio of the packing length of the mth catalyst layer to the packing length on the outlet side is z mHere, the packing length ratio is the percentage of the area occupied by each catalyst layer relative to the corresponding packing section. For example, in a two-layer packing with a total packing length of 200 cm, if the length of the first layer is 100 cm and the length of the second layer is 100 cm, then x1 is 50%, x2 is 50%, y1 is 100%, y2 is 0%, z1 is 0%, and z2 is 100%. Also, in a two-layer packing with a total packing length of 200 cm, if the length of the first layer is 50 cm and the length of the second layer is 150 cm, then x1 is 25%, x2 is 75%, y1 is 50%, y2 is 50%, z1 is 0%, and z2 is 100%. This can be generalized as y m , z m is expressed as follows: [Number 1] TIFF2026015556000001.tif163170

[0019] More preferred upper limits of the range of x1 are 90, 80, 70, 60, 50, 40, 37, 35, 34, 33.5, and 33.3, respectively, and more preferred lower limits are 10, 20, 25, 30, 31, 32, 32.5, and 32.9, respectively. That is, the most preferred range of x1 is 32.9 to 33.3, and particularly preferably greater than 32.9 and less than 33.3.

[0020] <Catalytic active component density A1, A2> The catalytically active component density (A1) of the inlet side catalyst and the catalytically active component density (A2) of the outlet side catalyst are derived as follows. For the catalyst packed in the i-th layer from the raw material inlet side, the catalyst loading rate b i , catalyst packing bulk density d ci , the packed bulk density d of the inert material used for dilution ui means the value calculated by the method described below. i is the catalyst packed in the ith layer, and e i means the catalyst weight dilution ratio represented by the formula (XII) described below. The density of the catalytic active component packed in the i-th layer from the raw material inlet side is a ci is derived. First, the catalyst volume dilution ratio f i Calculate [Number 2] TIFF2026015556000002.tif89170(VII) and (VIII) are used to calculate (A1 / A2).

[0021] More preferred upper limits of the (A1 / A2) range are 1.8, 1.7, 1.6, 1.5, 1.4, 1.35, 1.3, 1.27, 1.25, and 1.22, respectively, and more preferred lower limits are 1.15, 1.18, 1.19, and 1.20, respectively. That is, the most preferred range of (A1 / A2) is 1.20 to 1.22, and particularly preferably greater than 1.20 and less than 1.22. Furthermore, more preferable upper limits of the range of A1 are 1.0, 0.9, 0.8, 0.7, 0.65, 0.6, and 0.59, respectively, and the lower limits are 0.3, 0.4, 0.45, 0.5, and 0.55. That is, the most preferable range of A1 is 0.55 to 0.59, and particularly preferably greater than 0.55 and less than 0.59.

[0022] As an example, as shown in FIG. 1, a catalyst c1 having a catalyst loading rate of 60% and a catalyst loading bulk density of 1.2 g / ml is packed in a length of 20% of the total packing length from the raw gas inlet side at a catalyst weight dilution rate of 90% using an inert material u1 having a packing bulk density of 0.8 g / ml. Then, a catalyst c2 having a catalyst loading rate of 60% and a catalyst loading bulk density of 1.2 g / ml is packed without dilution in a length of 20% of the total packing length from the bottom side of the packed catalyst c1. 2. When catalyst c3 with a catalyst loading rate of 50% and a catalyst loading bulk density of 1.1 g / ml is packed undiluted over a length of 20% of the total packing length from the bottom side of the catalyst, and catalyst c4 with a catalyst loading rate of 40% and a catalyst loading bulk density of 1.0 g / ml is packed over a length of 40% of the total packing length from the bottom side of the packed catalyst c3 at a catalyst weight dilution rate of 70% using inert material u4 with a packing bulk density of 0.8 g / ml, A1 / A2 is calculated as follows: [Figure 1] TIFF2026015556000003.tif33170From formula (I), y1=40%, y2=40%, y3=20%, y4=0% From equation (V), f1=0.93, f2=1, f3=1, f4=0.74 From formula (VI), a c1 =0.67, a c2 =0.72, a c3 =0.55, a c4 =0.30 From equation (VII), A1 = 0.67 From formula (III), z1 = 0%, z2 = 0%, z3 = 20%, z4 = 80% From formula (VIII), A2 = 0.35 Therefore, A1 / A2=1.91

[0023] [Average catalyst particle size ratio (R1 / R2)] The production method of the present invention is a method of packing catalyst particles so that the ratio (R1 / R2) of the average catalyst particle size (R1) from the raw material gas inlet to halfway through the entire packing length to the average catalyst particle size (R2) from halfway through the entire packing length to the raw material gas outlet is 0.45 to 0.95.

[0024] <Catalytic active component density R1, R2> The derivation of the average catalyst particle diameters R1 and R2 will be explained. i , y m , z m is the same as that explained in A1 and A2. In addition, the average particle diameter of the catalyst packed in the i-th layer is r ci Let r ci means a value calculated by the method described below. Using formula (I), y of each layer i Calculate the obtained y i Using this, R1 is derived using the following formula: [Number 3] TIFF2026015556000004.tif52170

[0025] As an example, as shown in FIG. 1 above, a reaction tube is packed with catalyst c1 having an average particle size of 2.0 mm in a length that accounts for 20% of the total packing length from the raw material gas inlet side, catalyst c2 having an average particle size of 3.0 mm in a length that accounts for 20% of the total packing length from the bottom side of the packed catalyst c1, catalyst c3 having an average particle size of 4.0 mm in a length that accounts for 20% of the total packing length from the bottom side of the packed catalyst c2, and catalyst c4 having an average particle size of 5.0 mm in a length that accounts for 40% of the total packing length from the bottom side of the packed catalyst c3. R1 / R2 of this reaction tube is calculated as follows: From formula (I), y1 = 40%, y2 = 40%, y3 = 20%, y4 = 0% From equation (IX), R1 = 0.8 + 1.2 + 0.8 + 0 = 2.8 From formula (III), z1 = 0%, z2 = 0%, z3 = 20%, z4 = 80% From equation (X), R2 = 0 + 0 + 0.8 + 4.0 = 4.8 Therefore, R1 / R2=0.58

[0026] More preferable upper limits of the range of (R1 / R2) are 0.94, 0.93, 0.92, 0.91, 0.90, 0.89, and 0.88, respectively, and the lower limits are 0.5, 0.6, 0.7, 0.8, 0.84, and 0.86, respectively. That is, the most preferable range of (R1 / R2) is 0.86 to 0.88. Furthermore, more preferable upper limits of the range of R1 are 4.49, 4.4, 4.3, 4.2, 4.1, 4.0, and 3.9, respectively, and more preferable lower limits are 2.0, 2.5, 3.0, 3.2, 3.3, 3.4, 3.5, 3.6, and 3.7. That is, the most preferable range of A1 is 3.7 to 3.9, and particularly preferably greater than 3.7 and less than 3.9.

[0027] [Catalyst average particle size (r ci )] In the production method of the present invention, it is preferable that the catalyst particle size of the catalyst used on the inlet side, more preferably in the first layer, is 2.0 mm or more and 4.5 mm or less. The catalyst particle size is the number average of the three-axis mean diameter calculated from the average of the length (L), width (B), and thickness (T) of the catalyst. The three-axis mean diameter is calculated by the following formula (XI): [Formula 2] Triaxial average (mm) = (L+B+T) / 3 (XI) In the case of spherical catalysts, the length (L), width (B), and thickness (T) of the catalyst used to calculate the triaxial mean diameter are the length (L), width (B), and thickness (T) of the sample measured along three axes that pass through the center of gravity and intersect with each other, in descending order of diameter. The details of the measurements are not important as long as they are performed on a randomly sampled portion of the catalyst. For example, the average value is obtained by measuring 300 or more catalyst particles. The lower limit of the preferred catalyst particle size range is 2.0 mm, with more preferred lower limits being 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm, and 3.1 mm, respectively, and particularly preferably 3.3 mm. The preferred upper limit is 4.0 mm, with more preferred upper limits being 3.9 mm, 3.8 mm, and particularly preferably 3.7 mm. In other words, the most preferred range for the catalyst particle size is 3.3 mm or more and 3.7 mm or less. One of the features of the present invention is that the catalyst used on the inlet side has a smaller catalyst particle size than the catalyst used on the outlet side. That is, by using the catalyst on the inlet side with a particle size within the above range and smaller than the catalyst used on the outlet side, it is possible to realize an improvement in the maximum yield and an improvement in the yield in the high conversion region. When the catalyst used in the present invention is a supported catalyst, the catalyst particle size can be achieved by appropriately selecting the particle size of the carrier or adjusting the support rate. Furthermore, the catalyst of the present invention does not necessarily have to be spherical, and may be, for example, ring-shaped or cylindrical. When the catalyst is ring-shaped or cylindrical, the length (L), width (B), and thickness (T) of the catalyst used to calculate the triaxial mean diameter are defined as the vertical height (L) when placed with the circular portion facing downward, the width (B) when the sample is viewed from the side, and the depth (T) when the sample is viewed from the side. When an extrusion molding method is used for molding, the size of the mold used or cutting the extruded precursor to the desired length can be easily adjusted by those skilled in the art. When a tablet molding method is used, the size of the mold used or the molding pressure can be easily adjusted by those skilled in the art. Furthermore, even if the catalyst has another shape, the catalyst particle size is calculated using the three-axis mean diameter that is appropriate for the shape.

[0028] [Dilution of catalyst layer] The catalyst layer filled with an inert material such as an inert carrier can be diluted by mixing it with the molded catalyst. In this case, the average particle diameter r ci and catalytic active component density a ci The calculation is based on the average particle diameter r ci The inactive components are not included in the calculation because they do not affect the particle size of the catalyst. ci Since the value for varies depending on the volume occupied by the inert substance, it is calculated by taking into account the dilution rate according to formula (V). ci is derived.

[0029] [Catalyst weight dilution ratio of catalyst layer] When an inactive substance is mixed into the catalyst layer and diluted and packed, the catalyst c packed in the i-th layer i Catalyst weight dilution ratio e i is the catalyst c packed in the ith layer i Weight in g ci , catalyst c i The weight of the inert substance used to dilute is g ui Then, it can be calculated using the following formula: [Number 4] TIFF2026015556000005.tif20170 In the present invention, there is no particular limitation on the catalyst weight dilution ratio, but in order to extend the catalyst life, the lower limit of the preferred range of the catalyst weight dilution ratio is 40%, and more preferred lower limits are 50%, 60%, 70%, 80%, and 90%, respectively, and 100% (no dilution) is particularly preferred. The inert substance to be mixed is not particularly limited as long as it is substantially inert to the reaction, but examples thereof include silica, alumina, titania, zirconia, niobia, silicon carbide, and carbide. Examples of suitable materials include quartz, steatite, and composites thereof.

[0030] [Packed bulk density of catalyst and inactive components] The packed bulk density of the catalyst and inactive components is a value measured, for example, by the method described in JIS K 7365. That is, the measurement object is weighed into a 100 mL measuring cylinder, and the bulk density can be calculated from the mass of the 100 mL volume using the following formula. Packed bulk density = mass (g) packed into a 100 mL measuring cylinder / 100 In the present invention, the packed bulk density of the catalyst is not particularly limited as long as it satisfies A1 / A2. However, from the viewpoint of improving the reaction rate of the raw material compounds and the selectivity of the target compound, the lower limit of the packed bulk density of the catalyst used on the inlet side, more preferably in the first layer, is 0.60 g / cm. 3 and more preferable lower limits are 0.70 g / cm 3 , 0.80g / cm 3 , 0.90g / cm 3 , 1.00g / cm 3 , 1.10g / cm 3 and particularly preferably 1.20 g / cm 3 The preferred upper limit is 1.80 g / cm 3 and more preferable upper limits are 1.60 g / cm 3 , 1.50g / cm 3 and particularly preferably 1.40 g / cm 3 That is, the most preferable range for the packed bulk density of the catalyst is 1.20 g / cm 3 More than 1.40g / cm 3 The following is the result. The bulk density of the inert substance used to dilute the catalyst layer is preferably 0.5 to 1.5 times, more preferably 0.7 to 1.3 times, the bulk density of the catalyst to be diluted, from the viewpoint of uniform mixing with the catalyst.

[0031] [Catalyst composition] The catalyst used in the present invention preferably has a composition represented by the following formula (1) as an active component. [Formula 1] Mo a1 Bi b1 Ni c1 Co d1 Fe e1 X f1 Y g1Z h1 O i1 ···(1) (In the formula, Mo, Bi, Ni, Co, and Fe represent molybdenum, bismuth, nickel, cobalt, and iron respectively; X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium, and titanium; Y represents at least one element selected from sodium, potassium, cesium, rubidium, and thallium; Z belongs to Group 1 to Group 16 of the periodic table and means at least one element selected from elements other than the above Mo, Bi, Ni, Co, Fe, X, and Y; a1, b1, c1, d1, e1, f1, g1, h1, and i1 represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, X, Y, Z, and oxygen respectively. When a1 = 12, 0 < b1 ≤ 7.0, 0 ≤ c1 ≤ 10.0, 0 ≤ d1 ≤ 10.0, 0 < e1 ≤ 5.0, 0 ≤ f1 ≤ 2.0, 0 ≤ g1 ≤ 3.0, 0 ≤ h1 ≤ 5.0, and i1 is a value determined by the oxidation state of each element.)

[0032] In the above formula (1), when a1 = 12, the preferable ranges of b1 to h1 are as follows. The lower limits of b1 are preferably 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6 in order of preference, and particularly preferably 1.7. The upper limits are preferably 6, 5, 4, 3 in order of preference, and particularly preferably 2.5. That is, the most preferable range of b1 is 1.7 or more and 2.5 or less. The lower limits of c1 are preferably 0.2, 0.4, 0.5, 0.6, 0.8, 1.0, 1.2 in order of preference, and particularly preferably 1.4. The upper limits are preferably 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, 1.8 in order of preference, and particularly preferably 1.6. That is, the most preferable range of c1 is 1.4 or more and 1.6 or less. The lower limit of d1 is, in order of preference, 1.0, 2.0, 3.0, 4.0, and 5.0, and the upper limit is, in order of preference, 9.5, 9.0, 8.5, and 8.0, and particularly preferably 7.5. That is, the most preferred range for d1 is 5.0 or more and 7.5 or less. Note that c1+d1 also has a preferred range, with the lower limit being 0.0, 2.0, 4.0, 6.0, 8.0, and 8.3, in order of preference, and the upper limit being 20.0, 15.0, 12.5, 11.0, 10.0, and 9.0, in order of preference. In other words, the most preferred range for c1+d1 is 8.3 or more and 9.0 or less. The lower limit of e1 is, in order of preference, 0.10, 0.20, 0.50, 0.60, 0.80, and 1.00, with 1.10 being particularly preferred. The upper limit is, in order of preference, 1.65, 1.60, 1.55, 1.50, 1.45, 1.40, 1.35, 1.30, and 1.25, with 1.20 being particularly preferred. That is, the most preferred range for e1 is 1.10 or more and 1.20 or less. The upper limit of f1 is preferably 1.8, 1.5, 1.0, 0.8, and 0.5, in that order, and the lower limit is preferably 0. That is, the more preferable range for f1 is 0 or more and 0.5 or less, and 0 is most preferable. The lower limit of g1 is, in order of preference, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, and 0.16, with 0.18 being particularly preferred. The upper limit is, in order of preference, 2.5, 2.0, 1.5, 1.0, 0.8, 0.6, 0.5, 0.4, and 0.3, with 0.25 being particularly preferred. That is, the most preferred range for g1 is 0.18 or more and 0.25 or less. As Y, potassium, cesium, and rubidium are preferable, and cesium is most preferable. The upper limit of h1 is preferably 4.0, 3.0, 2.0, 1.8, 1.5, 1.0, 0.8, and 0.5, in that order, and the lower limit is preferably 0. That is, the more preferable range for h1 is 0 or more and 0.5 or less, and 0 is most preferable.

[0033] In the production method of the present invention, as long as the catalyst represented by the above formula (1) is used in any of the catalyst layers, the catalysts in the other catalyst layers are not particularly limited. However, it is preferable that the catalyst represented by the formula (1) is used in all layers, and it is more preferable that the catalyst used in the first layer has a composition described as the above preferred range for b1 to h1. The catalyst used in the second layer or later is preferably a catalyst having a composition represented by formula (1), and when a1=12, has the following b1 to h1. That is, The lower limit of b1 is preferably 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, and 1.4, and particularly preferably 1.6. The upper limit is preferably 6, 5, 4, 3, 2.5, and 2, and particularly preferably 1.8. That is, the most preferable range for b1 is 1.6 or more and 1.8 or less. The lower limit of c1 is preferably 0.2, 0.4, 0.5, and 0.6, with 0.7 being particularly preferred. The upper limit is preferably 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, 1.8, 1.6, 1.4, 1.2, and 1.0, with 0.9 being particularly preferred. That is, the most preferred range for c1 is 0.7 or more and 0.9 or less. The lower limit of d1 is, in order of preference, 1.0, 2.0, 3.0, 4.0, and 5.0, and the upper limit is, in order of preference, 9.5, 9.0, 8.5, and 8.0, and particularly preferably 7.5. That is, the most preferred range for d1 is 5.0 or more and 7.5 or less. There is also a preferred range for c1+d1, with the lower limit being 0.0, 2.0, 4.0, 6.0, and 7.0, and the upper limit being 20.0, 15.0, 12.5, 11.0, 10.0, and 9.0, in that order. In other words, the most preferred range for c1+d1 is 8.0 or more and 9.0 or less. The lower limit of e1 is, in order of preference, 0.10, 0.20, 0.50, 0.60, 0.80, 1.00, 1.20, 1.30, 1.40, 1.50, and 1.60, and is particularly preferably 1.70. The upper limit is, in order of preference, 3.00, 2.50, 2.00, and 1.90, and is particularly preferably 1.85. That is, the most preferred range for e1 is 1.70 or more and 1.85 or less. The upper limit of f1 is preferably 1.8, 1.5, 1.0, 0.8, and 0.5, in that order, and the lower limit is preferably 0. That is, the more preferable range for f1 is 0 or more and 0.5 or less, and 0 is most preferable. The lower limit of g1 is, in order of preference, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, and 0.13, with 0.14 being particularly preferred. The upper limit is, in order of preference, 2.5, 2.0, 1.5, 1.0, 0.8, 0.6, 0.5, 0.4, 0.3, and 0.2, with 0.16 being particularly preferred. That is, the most preferred range for g1 is 0.14 or more and 0.16 or less. As Y, potassium, cesium, and rubidium are preferable, and cesium is most preferable. The upper limit of h1 is preferably 4.0, 3.0, 2.0, 1.8, 1.5, 1.0, 0.8, and 0.5, in that order, and the lower limit is preferably 0. That is, the more preferable range for h1 is 0 or more and 0.5 or less, and 0 is most preferable.

[0034] [Loading rate] In the present invention, the support rate refers to the weight percentage of the catalytically active component contained in the catalyst molded body. When an inert substance is mixed before molding or when an inert component carrier is used to form a supported catalyst, the catalyst support rate is calculated using the following method. The catalyst of the present invention is not particularly limited in shape as long as the catalyst particle size and catalyst composition satisfy the above-mentioned conditions, and those molded into pillars, tablets, rings, spheres, etc. can be used. In addition, either a supported catalyst or an unsupported catalyst may be used. Note that, in order to make the effects of the present invention more pronounced, a spherical catalyst supported on an inert carrier is preferred. First, when calculating the loading rate for unsupported catalysts such as cylindrical, ring, or star-shaped catalysts, there are two ways to add the inert substance: adding it during blending or adding it to the dry granules. When adding it during blending, the catalyst loading rate can be calculated by performing elemental analysis on the granules obtained by drying the blend and calculating the weight percentage h of the active ingredient in the granule weight from the ratio. When adding it to the dry granules, the weight percentage j of the dry granules relative to the total weight of the dry granules and the inert substance can be calculated. Furthermore, when combining these methods of adding it during blending and adding it to the dry granules, the catalyst loading rate can be calculated by h × j / 100. When a supported catalyst is used, the catalyst support rate is calculated by the following formula, where k is the weight of the powder supported on the support and l is the weight of the support. Carrying rate=(k×h×j) / (k+l) / 100 In the present invention, the catalyst loading rate is not particularly limited as long as it satisfies A1 / A2, but from the viewpoint of improving the reaction rate of the raw material compounds, the lower limit of the catalyst loading rate of the catalyst used on the inlet side, more preferably in the first layer, is preferably 30%, 35%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, and 47%, in that order, and particularly preferably 48%. The upper limit is preferably 70%, 65%, 60%, 55%, 54%, and 53%, in that order, and particularly preferably 52%. Therefore, a loading rate of 48% or more but less than 52% is most preferred. As the material of the inert carrier, known materials such as alumina, silica, titania, zirconia, niobia, silica alumina, silicon carbide, carbide, steatite, and mixtures thereof can be used, but silica and / or alumina are preferred, and a mixture of silica and alumina is particularly preferred. It is preferable to use a binder for the support. 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. 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% by mass or more is preferred. The use of an appropriate amount of aqueous glycerin solution improves moldability, resulting in a high-performance catalyst with high mechanical strength. The amount of these binders used is typically 2 to 60 parts by mass per 100 parts by mass of the pre-calcined powder, with 20 to 50 parts by mass being preferred for the glycerin aqueous solution. During the support process, the binder and the pre-calcined powder may be supplied alternately or simultaneously to the molding machine.

[0035] [About catalyst manufacturing methods] The starting materials for the elements constituting the catalyst precursor and catalyst of the present invention are not particularly limited. For example, as the starting material for the molybdenum component, molybdenum oxides such as molybdenum trioxide, molybdic acid or a salt thereof such as molybdic acid, ammonium paramolybdate, and ammonium metamolybdate, and molybdenum-containing heteropolyacids or a salt thereof such as phosphomolybdic acid and silicomolybdic acid can be used.

[0036] As the raw material of the bismuth component, bismuth salts such as bismuth nitrate, bismuth carbonate, bismuth sulfate, and bismuth acetate, bismuth trioxide, metallic bismuth, etc. These raw materials can be used as solids, or as an aqueous solution, a nitric acid solution, or a slurry of a bismuth compound produced from these aqueous solutions, but it is preferable to use the nitrate, or a solution thereof, or a slurry produced from the solution.

[0037] The raw material of the alkali metal, which is the Y component represented by the general formula (1), is not limited to these, but examples thereof include hydroxides, chlorides, carbonates, sulfates, nitrates, oxides, and acetates of the component elements (lithium, sodium, potassium, rubidium, and cesium).Preferably, it is a compound containing cesium, such as cesium hydroxide, cesium chloride, cesium carbonate, cesium sulfate, and cesium oxide, with cesium nitrate being particularly preferred.

[0038] As the starting materials for the other component elements, ammonium salts, nitrates, nitrites, carbonates, subcarbonates, acetates, chlorides, inorganic acids, salts of inorganic acids, heteropolyacids, salts of heteropolyacids, sulfates, hydroxides, organic acid salts, oxides, or mixtures thereof of metal elements generally used in this type of catalyst may be used in combination, with ammonium salts and nitrates being preferred.

[0039] These active ingredient-containing compounds may be used alone or in a mixture of two or more. The slurry can be obtained by uniformly mixing each active ingredient-containing compound with water. There are no particular restrictions on the amount of water used in the slurry, as long as it can completely dissolve all of the compounds used or can be uniformly mixed. The amount of water used can be determined appropriately taking into account the drying method and drying conditions. Typically, the amount of water used is 200 to 2,000 parts by mass per 100 parts by mass of the total mass of the compounds used to prepare the slurry. While a larger amount of water is preferable, too much water has many disadvantages, such as increased energy costs in the drying process and incomplete drying. Furthermore, the nitrate ion concentration in the slurry liquid immediately before final drying is 8.0 mass% or more and 50 mass% or less, preferably 9.0 mass% or more and 45 mass% or less, more preferably 10.0 mass% or more and 40 mass% or less, and most preferably 11.0 mass% or more and 30 mass% or less. Similarly, the ammonium ion concentration in the slurry liquid immediately before drying is 1.0 mass% or more and 10 mass% or less, preferably 1.2 mass% or more and 8 mass% or less, more preferably 1.5 mass% or more and 6 mass% or less, and most preferably 1.7 mass% or more and 4 mass% or less.

[0040] The slurry of the source compounds of the above-mentioned component elements is preferably prepared by (a) mixing the source compounds all at once, (b) mixing them all at once followed by aging, (c) mixing them stepwise, (d) repeating the mixing and aging stepwise, or a combination of (a) to (d). Here, aging refers to "processing industrial raw materials or semi-finished products under specific conditions, such as a fixed time and a fixed temperature, to obtain or enhance required physical or chemical properties or to promote a desired reaction." In the present invention, the fixed time refers to a range of 5 minutes to 24 hours, and the fixed temperature refers to a range above room temperature and below the boiling point of the aqueous solution or dispersion. Among these, the stepwise mixing method (c) is preferred in terms of the activity and yield of the final catalyst. More preferred is a method in which the raw materials are mixed stepwise into a mother liquor in a completely dissolved state. Most preferred is a method in which an alkali metal solution and various mixtures of nitrates are mixed into a mother liquor prepared as a blend or slurry of the molybdenum raw material.

[0041] In the present invention, there are no particular restrictions on the shape of the stirring blades of the stirrer used when mixing the essential active ingredients, and any stirring blades such as propeller blades, turbine blades, paddle blades, inclined paddle blades, screw blades, anchor blades, ribbon blades, large lattice blades, etc. can be used in one stage or in two or more stages of the same or different blades in the vertical direction. In addition, baffles (baffle plates) may be installed in the reaction vessel as necessary.

[0042] The slurry thus obtained is then dried. The drying method is not particularly limited as long as it can completely dry the slurry, and examples thereof include drum drying, freeze drying, spray drying, and evaporation to dryness. Among these, spray drying is particularly preferred in the present invention, as it can dry the slurry into powder or granules in a short time. The drying temperature for spray drying varies depending on the concentration of the slurry, the liquid delivery speed, etc., but the temperature at the outlet of the dryer is generally between 70°C and 150°C.

[0043] The catalyst precursor obtained as described above can be molded and then calcined, thereby controlling and maintaining the molded shape, thereby obtaining a catalyst with particularly excellent mechanical strength for industrial applications and exhibiting stable catalytic performance. If necessary, a pre-calcination step may be carried out before molding.

[0044] The pre-calcination (calcination of the catalyst precursor before molding) method and conditions, or the main calcination (calcination after molding) method and 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 material, catalyst composition, preparation method, etc., used. However, they are typically performed under a flow of oxygen-containing gas such as air or an inert gas at 200°C to 600°C, preferably 300°C to 550°C, for 0.5 hours or more, preferably 1 hour to 40 hours. Here, the term "inert gas" refers to a gas that does not reduce the catalytic activity, and specific examples include nitrogen, carbon dioxide, helium, and argon. The main calcination is particularly important in determining the catalytic activity of the present invention. However, when the catalytic activity is low or high, it is well known to those skilled in the art to adjust the activity by changing the process parameters of the main calcination step, such as the oxygen content in the atmosphere, the maximum temperature, and the calcination time, to maximize the yield of the composition. This is within the scope of the present invention. The firing step is carried out after the pre-firing step, and the maximum temperature reached in the firing step (firing temperature) is higher than the maximum temperature reached in the pre-firing step (pre-firing temperature). The upper limit of the calcination temperature in the catalyst production method of the present invention is, in order of preference, 600°C, 540°C, 530°C, and 520°C, with 515°C being particularly preferred. The lower limit is, in order of preference, 450°C, 480°C, 490°C, 500°C, and 505°C, with 510°C being particularly preferred. In other words, the most preferred range for the calcination temperature is 510°C or higher and 515°C or lower.

[0045] The catalyst of the present invention is preferably used as a catalyst for producing an unsaturated aldehyde compound or an unsaturated carboxylic acid compound, more preferably used as a catalyst for the first stage, i.e., for producing an unsaturated aldehyde compound, and particularly preferably used as a catalyst for producing methacrolein from isobutylene.

[0046] [About the second stage catalyst] When an unsaturated aldehyde compound is produced by the production method of the present invention, an unsaturated carboxylic acid compound can be obtained by carrying out a second-stage oxidation reaction. In this case, the second stage catalyst is preferably a catalyst represented by the following formula (2). Mo 10 V A2 P b2 Cu c2 Cs d2 (NH4) e2 X f2 O g2 (2) (In the formula, Mo represents molybdenum, V represents vanadium, P represents phosphorus, Cu represents copper, Cs represents cesium, (NH4) represents an ammonium group, 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, A2 represents a positive number in the range of 0.1≦A2≦6.0, b2 represents a positive number in the range of 0.5≦b2≦6.0, c2 represents a positive number in the range of 0≦c2≦3.0, d2 represents a positive number in the range of 0≦d2≦3.0, e2 represents a positive number in the range of 0≦e2≦3.0, and f2 represents a positive number in the range of 0≦f2≦3.0. g2 is a value determined by the valence of each element.)

[0047] In producing the catalyst represented by the above formula (2), a method generally known as a method for preparing this type of catalyst, such as an oxide catalyst or a catalyst having a heteropolyacid or its salt structure, can be used. There are no particular restrictions on the raw materials that can be used in producing the catalyst, and various materials can be used. For example, usable molybdenum compounds include ammonium molybdate, molybdic acid, and molybdenum oxide; usable vanadium compounds include ammonium metavanadate and vanadium pentoxide; usable phosphorus compounds include phosphoric acid or a salt thereof, and polymerized phosphoric acid or a salt thereof; usable copper compounds include copper oxide, copper phosphate, copper sulfate, copper nitrate, copper molybdate, and copper metal; and usable antimony, arsenic, silver, magnesium, zinc, aluminum, boron, germanium, tin, lead, titanium, zirconium, chromium, rhenium, bismuth, tungsten, iron, cobalt, nickel, cerium, thorium, potassium, and rubidium compounds include their respective nitrates, sulfates, carbonates, phosphates, organic acid salts, halides, hydroxides, oxides, and metals.

[0048] These compounds containing active ingredients may be used alone or in combination of two or more.

[0049] The resulting slurry is then dried to form a solid catalytically active component. The drying method is not particularly limited as long as it can completely dry the slurry, and examples include drum drying, freeze drying, spray drying, and evaporation to dryness. Spray drying is preferred, as it can dry the slurry into powder or granules in a short time. The drying temperature for spray drying varies depending on the concentration of the slurry, the liquid delivery speed, etc., but the temperature at the outlet of the dryer is generally 70 to 150°C. Furthermore, drying is preferably performed so that the average particle size of the resulting dried slurry is 1 to 700 μm, and more preferably 5 to 500 μm.

[0050] Among the second-stage catalytically active solid components of the present invention, a catalyst having a heteropolyacid structure is particularly preferred. This catalyst has a basic skeleton of phosphovanadomolybdic acid, and other constituent elements are incorporated into this heteropolyacid structure, which is thought to contribute to improving catalytic activity and selectivity as well as improving the thermal stability of the structure. This catalyst has a particularly long life. This catalyst can be easily prepared by a common method for preparing ordinary heteropolyacids.

[0051] The second-stage catalytically active component solid obtained as described above can be used as a coating mixture as is, but calcining it may improve moldability and is therefore preferable. The calcination method and conditions are not particularly limited, and known processing methods and conditions can be applied. The optimal calcination conditions vary depending on the catalyst raw material, catalyst composition, preparation method, etc. used, but the calcination temperature is usually 100 to 350°C, preferably 150 to 300°C, and the calcination time is 1 to 20 hours. Calcination is usually carried out in an air atmosphere, but it may also be carried out in an inert gas atmosphere such as nitrogen, carbon dioxide, helium, or argon, or, if necessary, calcination in an inert gas atmosphere may be followed by further calcination in an air atmosphere.

[0052] In the present invention, the compound containing the active ingredient used in preparing the second-stage slurry does not necessarily contain all of the active ingredient, and some of the ingredients may be used before the coating step described below.

[0053] The shape of the second-stage catalyst of the present invention is not particularly limited, and it can be molded into pillars, tablets, rings, spheres, etc., to reduce the pressure loss of the reaction gas during the oxidation reaction. Among these, it is particularly preferred to coat an inert carrier with a solid catalytically active component to form a coated catalyst, as this is expected to improve selectivity and remove reaction heat. The coating step is preferably the tumbling granulation method described below. This method involves, for example, rotating a flat or uneven disk at the bottom of a fixed container at high speed in an apparatus, thereby vigorously agitating the carrier in the container through repeated rotation and revolution, and then coating the carrier with a coating mixture containing a binder, a solid catalytically active component, and, if necessary, other additives, such as a molding aid or strength improver. The binder can be added in any of the following ways: 1) premixing with the coating mixture; 2) adding simultaneously with the addition of the coating mixture to the fixed container; 3) adding after the coating mixture is added to the fixed container; 4) adding before the coating mixture is added to the fixed container; or 5) dividing the coating mixture and binder into separate parts and adding the entire amount by combining methods 2) to 4). Of these, method 5) is preferably carried out by adjusting the addition rate using an autofeeder or the like so that the desired amount of the coating mixture is supported on the support without adhesion to the fixed container wall or aggregation of the coating mixture. The binder is not particularly limited as long as it is at least one selected from the group consisting of water and organic compounds with a boiling point of 150°C or less at 1 atmosphere or less. Specific examples of binders other than water include alcohols such as methanol, ethanol, propanols, and butanols, preferably alcohols with 1 to 4 carbon atoms; ethers such as ethyl ether, butyl ether, and dioxane; esters such as ethyl acetate and butyl acetate; ketones such as acetone and methyl ethyl ketone; and aqueous solutions of these. Ethanol is particularly preferred. When ethanol is used as a binder, the ethanol / water ratio is preferably 10 / 0 to 0 / 10 (mass ratio), and is preferably mixed with water to give a mass ratio of 9 / 1 to 1 / 9. The amount of the binder used is usually 2 to 60 parts by mass, and preferably 10 to 50 parts by mass, per 100 parts by mass of the coating mixture.

[0054] Specific examples of the carrier for the coating include spherical carriers having a diameter of 1 to 15 mm, preferably 2.5 to 10 mm, such as silicon carbide, alumina, silica alumina, mullite, and alundum. These carriers typically have a porosity of 10 to 70%. The ratio of the carrier to the coating mixture is typically 10 to 75% by mass, preferably 15 to 60% by mass, of the coating mixture / (coating mixture + carrier). When the ratio of the coating mixture is high, the reactivity of the coated catalyst tends to be high, but the mechanical strength tends to be low. Conversely, when the ratio of the coating mixture is low, the mechanical strength tends to be high, but the reactivity tends to be low. Examples of molding aids that may be used as needed include silica gel, diatomaceous earth, and alumina powder. The amount of molding aid used is typically 1 to 60 parts by mass per 100 parts by mass of the solid catalytically active component. Furthermore, if necessary, the use of inorganic fibers (e.g., ceramic fibers or whiskers) that are inert to the catalytically active component solids and reaction gases as a strength improver is useful for improving the mechanical strength of the catalyst, and glass fibers are preferred. The amount of these fibers used is usually 1 to 30 parts by mass per 100 parts by mass of the catalytically active component solids. In the first-stage catalyst molding, the molding aids, pore-forming agents, and carriers added are not considered to be constituent elements of the active component in the present invention, regardless of whether they are active in converting the raw materials into some other product.

[0055] The coated catalyst obtained as described above can be used directly in a gas-phase catalytic oxidation reaction, but calcination is preferable because it may improve catalytic activity. The calcination method and conditions are not particularly limited, and known treatment methods and conditions can be applied. The optimal calcination conditions vary depending on the catalyst raw material used, catalyst composition, preparation method, etc., but the calcination temperature is usually 100 to 450°C, preferably 270 to 420°C, and the calcination time is 1 to 20 hours. Calcination is usually carried out in an air atmosphere, but it may also be carried out in an inert gas atmosphere such as nitrogen, carbon dioxide, helium, or argon. After calcination in an inert gas atmosphere, calcination may be further carried out in an air atmosphere if necessary. By supporting the catalyst used in the present invention on a carrier, desirable effects such as improved heat resistance, lifespan, and reaction yield can be expected. As the material of the carrier, known materials such as alumina, silica, titania, zirconia, niobia, silica alumina, silicon carbide, carbides, and mixtures thereof can be used. Furthermore, there are no particular limitations on the particle size, water absorption rate, mechanical strength, crystallinity of each crystalline phase, or mixing ratio, and appropriate ranges should be selected taking into consideration the performance, moldability, production efficiency, etc. of the final catalyst.

[0056] The production method of the present invention, in the reaction of producing the corresponding unsaturated aldehyde or unsaturated carboxylic acid from raw materials such as propylene, isobutylene, or t-butyl alcohol, particularly the reaction of producing methacrolein or methacrylic acid by vapor-phase catalytic oxidation of isobutylene or t-butyl alcohol with molecular oxygen or a molecular oxygen-containing gas, achieves high yields in a range of high raw material conversion compared to known methods, and is expected to improve the price competitiveness of the product. The production method of the present invention is also effective in improving yields even in a range of low raw material conversion. Furthermore, the production method of the present invention is also effective in reducing by-products that have adverse effects on the environment and the quality of the final product, methyl methacrylate, such as carbon monoxide (CO), carbon dioxide (CO), acetaldehyde, acetic acid, acrolein, and formaldehyde.

[0057] In the production method of the present invention, the method of flowing the raw material gas may be a normal single flow method or a recycle method, and can be carried out under commonly used conditions and is not particularly limited. For example, a mixed gas consisting of 1 to 10 vol%, preferably 4 to 9 vol%, more preferably 4 to 7.5 vol%, and most preferably 5 to 7 vol% of isobutylene as a starting raw material at room temperature, 3 to 20 vol%, preferably 4 to 18 vol%, molecular oxygen, 0 to 60 vol%, preferably 4 to 50 vol% of water vapor, and 20 to 80 vol%, preferably 30 to 60 vol% of an inert gas such as carbon dioxide or nitrogen, is passed over the catalyst of the present invention filled in a reaction tube at 250 to 450°C under a pressure of normal pressure to 10 atmospheres at a space velocity of 300 to 5000 h -1 and the reaction is carried out.

[0058] In the present invention, the region where the raw material conversion rate is high refers to a region where the raw material conversion rate is 99.0% or higher. While it is usually difficult to maintain a high yield in a region where the raw material conversion rate is high, the production method of the present invention makes it possible to maintain a high yield. Furthermore, this raw material conversion rate is preferably 99.1% or higher, more preferably 99.2% or higher, even more preferably 99.3% or higher, particularly preferably 99.4% or higher, and most preferably 99.5% or higher. Therefore, in the production of unsaturated aldehydes using the production method of the present invention, it is possible to obtain the target product in a higher yield than conventional production methods, even when the raw material conversion rate is increased to 99.5%. As described in the examples, the present production method is also capable of obtaining the target product in a high yield even in a region where the raw material conversion rate is not high. In the present invention, unless otherwise specified, a high yield means that the total yield of methacrolein and / or methacrylic acid is high in a range where the raw material conversion rate is high. In the present invention, unless otherwise specified, the constituent elements of the catalytically active component refer to all elements contained in the catalyst raw material solution and catalyst raw material slurry containing molybdenum as the main component prior to the drying step in the catalyst production process. However, inactive substances such as alumina, silica, titania, zirconia, niobia, silica-alumina, silicon carbide, carbides, and steatite, as well as raw materials and their constituent elements that disappear, sublimate, volatilize, or burn at temperatures below 200°C, are not included in the constituent elements of the active component of the catalyst. In the present invention, the unsaturated aldehyde and unsaturated aldehyde compound are organic compounds having at least one double bond and at least one aldehyde in the molecule, such as acrolein and methacrolein, while the unsaturated carboxylic acid and unsaturated carboxylic acid compound are organic compounds having at least one double bond and at least one carboxyl group or its ester group in the molecule, such as acrylic acid, methacrylic acid, and methyl methacrylate. [Example]

[0059] The present invention will be described in more detail below with reference to examples. In the examples, the conversion rate, yield, selectivity and loading rate were calculated according to the following formulas. Raw material conversion rate (%) = (number of moles of reacted t-butyl alcohol or isobutylene) / ( (number of moles of t-butyl alcohol or isobutylene supplied) × 100 Effective yield (%) = (total number of moles of methacrolein and methacrylic acid produced) / (feed (number of moles of t-butyl alcohol or isobutylene added) x 100 Loading rate (mass%) = (mass of pre-calcined powder used for molding) / {(mass of pre-calcined powder used for molding)} (Mass of powder) + (Mass of carrier used for molding) × 100

[0060] (Preparation of Catalyst 1) 100 parts by mass of ammonium heptamolybdate was completely dissolved in 380 parts by mass of pure water heated to 80°C (mother liquor 1). Next, 1.8 parts by mass of cesium nitrate was dissolved in 16 parts by mass of pure water and added to mother liquor 1. Next, 23 parts by mass of ferric nitrate, 100 parts by mass of cobalt nitrate, and 21 parts by mass of nickel nitrate were dissolved in 76 parts by mass of pure water heated to 60°C and added to mother liquor 1. Subsequently, 50 parts by mass of bismuth nitrate was dissolved in an aqueous nitric acid solution prepared by adding 13 parts by mass of nitric acid (60% by mass) to 53 parts by mass of pure water heated to 60°C, and added to mother liquor 1. This mother liquor 1 was dried by a spray-drying method, and the obtained dried powder was pre-calcined at 440°C for 5 hours. To the pre-calcined powder thus obtained (atomic ratio calculated from the charged raw materials: Mo:Bi:Fe:Co:Ni:Cs = 12:2.2:1.2:7.3:1.5:0.2), 5% by mass of crystalline cellulose was added and thoroughly mixed. After thorough mixing, the powder was granulated by a tumbling method using 40% by mass of a 25% by mass glycerin solution as a binder, and the granules were formed into spheres on a 3.0 mm silica-alumina support to achieve a loading rate of 50% by mass. The spherical shaped product thus obtained was calcined at 510°C for 5 hours to obtain Catalyst 1 with a catalyst particle size of 3.5 mm and a packed bulk density of 1.25 g / mL.

[0061] (Preparation of Catalyst 2) The pre-calcined powder obtained by preparing catalyst 1 was used, and 5% by mass of crystalline cellulose was added to the pre-calcined powder and thoroughly mixed. Then, using a tumbling granulation method, 40% by mass of a 25% by mass glycerin solution was used as a binder to form spheres on a 2.8 mm silica-alumina support to achieve a loading rate of 50% by mass. The spherical shaped product thus obtained was calcined at 520°C for 5 hours to obtain catalyst 2 with a catalyst particle size of 3.2 mm and a packed bulk density of 1.32 g / mL.

[0062] (Preparation of Catalyst 3) The pre-calcined powder obtained by preparing catalyst 1 was used to add 5% by mass of crystalline cellulose to the pre-calcined powder, and after thorough mixing, the mixture was granulated by a tumbling method using 40% by mass of a 25% by mass glycerin solution as a binder, and formed into spheres on a 3.0 mm silica-alumina support to achieve a loading rate of 60% by mass. The spherical shaped product thus obtained was calcined at 530°C for 5 hours to obtain catalyst 3 with a catalyst particle size of 3.8 mm and a packed bulk density of 1.24 g / mL.

[0063] (Preparation of Catalyst 4) 100 parts by mass of ammonium heptamolybdate was completely dissolved in 380 parts by mass of pure water heated to 80°C (mother liquor 1). Next, 1.4 parts by mass of cesium nitrate was dissolved in 16 parts by mass of pure water and added to mother liquor 1. Next, 19 parts by mass of ferric nitrate, 99 parts by mass of cobalt nitrate, and 11 parts by mass of nickel nitrate were dissolved in 68 parts by mass of pure water heated to 60°C and added to mother liquor 1. Subsequently, 38 parts by mass of bismuth nitrate was dissolved in an aqueous nitric acid solution prepared by adding 10 parts by mass of nitric acid (60% by mass) to 41 parts by weight of pure water heated to 60°C, and added to mother liquor 1. This mother liquor 1 was dried by a spray-drying method, and the resulting dried powder was pre-calcined at 440°C for 5 hours. To the pre-calcined powder thus obtained (atomic ratio calculated from the charged raw materials: Mo:Bi:Fe:Co:Ni:Cs = 12:1.7:1.0:7.2:0.8:0.15), 5% by mass of crystalline cellulose was added and thoroughly mixed. After that, using a tumbling granulation method, 25% by mass of glycerin solution was used as a binder (40% by mass relative to the pre-calcined powder), and the pre-calcined powder was shaped into spheres so that the loading rate was 50% by mass on a 3.0 mm silica-alumina support. The spherical shaped product thus obtained was calcined at 510 °C for 5 hours to obtain catalyst 4 with a catalyst particle size of 3.5 mm and a packed bulk density of 1.21 g / mL.

[0064] (Preparation of Catalyst 5) 100 parts by mass of ammonium heptamolybdate was completely dissolved in 380 parts by mass of pure water heated to 80°C (mother liquor 1). Next, 1.4 parts by mass of cesium nitrate was dissolved in 16 parts by mass of pure water and added to mother liquor 1. Next, 23 parts by mass of ferric nitrate, 99 parts by mass of cobalt nitrate, and 11 parts by mass of nickel nitrate were dissolved in 70 parts by mass of pure water heated to 60°C and added to mother liquor 1. Subsequently, 38 parts by mass of bismuth nitrate was dissolved in an aqueous nitric acid solution prepared by adding 10 parts by mass of nitric acid (60% by mass) to 41 parts by weight of pure water heated to 60°C, and added to mother liquor 1. This mother liquor 1 was dried by a spray-drying method, and the resulting dried powder was pre-calcined at 440°C for 5 hours. To the pre-calcined powder thus obtained (atomic ratio calculated from the charged raw materials: Mo:Bi:Fe:Co:Ni:Cs = 12:1.7:1.2:7.2:0.8:0.15), 5% by mass of crystalline cellulose was added and thoroughly mixed, and then the mixture was granulated by a rolling granulation method using 40% by mass of a 25% by mass glycerin solution as a binder relative to the pre-calcined powder, and the mixture was shaped into spheres on a 3.0 mm silica-alumina support to achieve a loading rate of 50% by mass. The spherical shaped product thus obtained was calcined at 510 °C for 5 hours to obtain catalyst 5 with a catalyst particle size of 3.5 mm and a packed bulk density of 1.21 g / mL.

[0065] (Preparation of Catalyst 6) 100 parts by mass of ammonium heptamolybdate was completely dissolved in 380 parts by mass of pure water heated to 80°C (mother liquor 1). Next, 1.4 parts by mass of cesium nitrate was dissolved in 16 parts by mass of pure water and added to mother liquor 1. Next, 25 parts by mass of ferric nitrate, 99 parts by mass of cobalt nitrate, and 11 parts by mass of nickel nitrate were dissolved in 71 parts by mass of pure water heated to 60°C and added to mother liquor 1. Subsequently, 38 parts by mass of bismuth nitrate was dissolved in an aqueous nitric acid solution prepared by adding 10 parts by mass of nitric acid (60% by mass) to 41 parts by weight of pure water heated to 60°C, and added to mother liquor 1. This mother liquor 1 was dried by a spray-drying method, and the resulting dried powder was pre-calcined at 440°C for 5 hours. To the pre-calcined powder thus obtained (atomic ratio calculated from the raw materials: Mo:Bi:Fe:Co:Ni:Cs = 12:1.7:1.3:7.2:0.8:0.15), 5% by mass of crystalline cellulose was added and thoroughly mixed. After thorough mixing, the powder was granulated by a tumbling method using 40% by mass of a 25% by mass glycerin solution as a binder, and the granules were formed into spheres on a 3.0 mm silica-alumina support to achieve a loading rate of 50% by mass. The spherical shaped product thus obtained was calcined at 520°C for 5 hours to obtain catalyst 6 with a catalyst particle size of 3.5 mm and a packed bulk density of 1.23 g / mL.

[0066] (Preparation of Catalyst 7) 100 parts by mass of ammonium heptamolybdate was completely dissolved in 380 parts by mass of pure water heated to 80°C (mother liquor 1). Next, 1.4 parts by mass of cesium nitrate was dissolved in 16 parts by mass of pure water and added to mother liquor 1. Next, 34 parts by mass of ferric nitrate, 99 parts by mass of cobalt nitrate, and 11 parts by mass of nickel nitrate were dissolved in 76 parts by mass of pure water heated to 60°C and added to mother liquor 1. Subsequently, 38 parts by mass of bismuth nitrate was dissolved in an aqueous nitric acid solution prepared by adding 10 parts by mass of nitric acid (60% by mass) to 41 parts by mass of pure water heated to 60°C, and added to mother liquor 1. This mother liquor 1 was dried by spray drying, and the resulting dried powder was pre-calcined at 440°C for 5 hours. To the pre-calcined powder thus obtained (atomic ratio calculated from the raw materials: Mo:Bi:Fe:Co:Ni:Cs = 12:1.7:1.8:7.2:0.8:0.15), 5% by mass of crystalline cellulose was added and thoroughly mixed. After that, the pre-calcined powder was granulated by a tumbling method using 40% by mass of a 25% by mass glycerin solution as a binder, and the pre-calcined powder was shaped into spheres so that the loading rate was 50% by mass on a 3.0 mm silica-alumina support. The spherical shaped product thus obtained was calcined at 520°C for 5 hours to obtain Catalyst 7 with a catalyst particle size of 3.5 mm and a packed bulk density of 1.26 g / mL.

[0067] (Preparation of Catalyst 8) The pre-calcined powder obtained in the preparation of catalyst 7 was used to add 5% by mass of crystalline cellulose to the pre-calcined powder, and after thorough mixing, the mixture was granulated by a tumbling method using 40% by mass of a 25% by mass glycerin solution as a binder, and formed into spheres on a 3.8 mm silica-alumina support to achieve a loading rate of 50% by mass. The spherical shaped product thus obtained was calcined at 520°C for 5 hours to obtain catalyst 8 with a catalyst particle size of 4.4 mm and a packed bulk density of 1.19 g / mL.

[0068] (Preparation of Catalyst 9) The pre-calcined powder obtained in the preparation of catalyst 7 was used to add 5% by mass of crystalline cellulose to the pre-calcined powder, and after thorough mixing, the mixture was granulated by a tumbling method using 40% by mass of a 25% by mass glycerin solution as a binder, and formed into spheres on a 4.0 mm silica-alumina support to achieve a loading rate of 40% by mass. The spherical shaped product thus obtained was calcined at 520°C for 5 hours to obtain catalyst 9 with a catalyst particle size of 4.4 mm and a packed bulk density of 1.18 g / mL.

[0069] (Preparation of Catalyst 10) 100 parts by mass of ammonium heptamolybdate was completely dissolved in 380 parts by mass of pure water heated to 80°C (mother liquor 1). Next, 3.7 parts by mass of cesium nitrate was dissolved in 42 parts by mass of pure water and added to mother liquor 1. Next, 34 parts by mass of ferric nitrate, 99 parts by mass of cobalt nitrate, and 11 parts by mass of nickel nitrate were dissolved in 76 parts by mass of pure water heated to 60°C and added to mother liquor 1. Subsequently, 38 parts by mass of bismuth nitrate was dissolved in an aqueous nitric acid solution prepared by adding 10 parts by mass of nitric acid (60% by mass) to 41 parts by weight of pure water heated to 60°C, and added to mother liquor 1. This mother liquor 1 was dried by a spray-drying method, and the resulting dried powder was pre-calcined at 440°C for 5 hours. To the pre-calcined powder thus obtained (atomic ratio calculated from the charged raw materials: Mo:Bi:Fe:Co:Ni:Cs = 12:1.7:1.8:7.2:0.8:0.40), 5% by mass of crystalline cellulose was added and thoroughly mixed, and then the mixture was granulated by a tumbling method using 40% by mass of a 25% by mass glycerin solution as a binder relative to the pre-calcined powder, and the mixture was shaped into spheres on a 4.0 mm silica-alumina support to achieve a loading rate of 40% by mass. The spherical shaped product thus obtained was calcined at 505°C for 5 hours to obtain catalyst 10 with a catalyst particle size of 4.4 mm and a packed bulk density of 1.20 g / mL.

[0070] (Preparation of Catalyst 11) The pre-calcined powder obtained in the preparation of catalyst 7 was used, and 5% by mass of crystalline cellulose was added to the pre-calcined powder and thoroughly mixed. Then, using a tumbling granulation method, 40% by mass of a 25% by mass glycerin solution as a binder was used to form spheres on a 3.8 mm silica-alumina support to achieve a loading rate of 70% by mass. The spherical shaped product thus obtained was calcined at 510°C for 5 hours to obtain catalyst 11 with a catalyst particle size of 5.3 mm and a packed bulk density of 1.14 g / mL.

[0071] (Production of methacrolein and methacrylic acid) The catalyst obtained by the above preparation method was evaluated for reactivity by the following method. A total of 40.6 mL of catalyst, including inert diluents, was packed into a stainless steel reactor tube. The catalyst was then aged for at least 200 hours at a bath temperature of 350°C under conditions of an outlet pressure of 50 kPaG, a GHSV of 1000 hr-1, and a TOS of 1:2.2:1.6:1.9. The aging reaction was then carried out at a temperature of 350°C and a condenser at the reactor outlet. The gas and condensate components were separated using a gas chromatograph equipped with a flame ionization detector and a thermal conductivity detector, respectively. The data obtained by gas chromatography were factor-corrected to calculate the feed conversion and effective yield.

[0072] [Example 1] Catalyst layers were installed in the reaction tube in the following order from the raw material gas inlet side to the raw material gas outlet side. Catalyst 1 was packed in the first catalyst layer (on the raw material gas inlet side) at 33% of the total packing length, and catalyst 9 was packed in the second catalyst layer at 67% of the total packing length, resulting in a two-layer catalyst layer. The A1 / A2, R1 / R2, and evaluation results of the catalyst layers thus formed are shown in Table 1.

[0073] [Example 2] The procedure was the same as in Example 1, except that catalyst 2 was used instead of catalyst 1. The A1 / A2 and R1 / R2 ratios of the catalyst layers thus formed and the evaluation results are shown in Table 1.

[0074] [Example 3] The procedure was the same as in Example 1, except that catalyst 3 was used instead of catalyst 1. The A1 / A2 and R1 / R2 ratios of the catalyst layers thus formed and the evaluation results are shown in Table 1.

[0075] [Example 4] The procedure was the same as in Example 1, except that catalyst 4 was used instead of catalyst 1. The A1 / A2 and R1 / R2 ratios of the catalyst layers thus formed and the evaluation results are shown in Table 1.

[0076] [Example 5] The procedure was the same as in Example 1, except that catalyst 5 was used instead of catalyst 1. The A1 / A2 and R1 / R2 ratios of the catalyst layers thus formed and the evaluation results are shown in Table 1.

[0077] [Example 6] The procedure was the same as in Example 1, except that catalyst 6 was used instead of catalyst 1. The A1 / A2 and R1 / R2 ratios of the catalyst layers thus formed and the evaluation results are shown in Table 1.

[0078] [Example 7] The procedure was the same as in Example 1, except that catalyst 7 was used instead of catalyst 1. The A1 / A2 and R1 / R2 ratios of the catalyst layers thus formed and the evaluation results are shown in Table 1.

[0079] [Example 8] The procedure was the same as in Example 1, except that catalyst 8 was used instead of catalyst 1. The A1 / A2 and R1 / R2 ratios of the catalyst layers thus formed and the evaluation results are shown in Table 1.

[0080] [Comparative Example 1] The catalyst layer was constructed as a single layer by filling 100% of the total filling length with catalyst 9. The A1 / A2, R1 / R2 and evaluation results of the catalyst layer thus formed are shown in Table 1.

[0081] Comparative Example 2 The procedure was the same as in Example 1, except that catalyst 8 was used instead of catalyst 9. The A1 / A2 and R1 / R2 ratios of the catalyst layer thus formed and the evaluation results are shown in Table 1.

[0082] Comparative Example 3 The catalyst layer had a two-layer structure, with catalyst 10 filling 50% of the total packing length as the first catalyst layer (feed gas inlet side) and catalyst 8 filling 50% of the total packing length as the second catalyst layer. The A1 / A2, R1 / R2, and evaluation results of the catalyst layers thus formed are shown in Table 1.

[0083] Comparative Example 4 The catalyst layer had a two-layer structure, with catalyst 9 filling 50% of the total packing length as the first catalyst layer (feed gas inlet side) and catalyst 11 filling 50% of the total packing length as the second catalyst layer. The A1 / A2, R1 / R2, and evaluation results of the catalyst layers thus formed are shown in Table 1. [Table 1]

[0084] As is clear from Table 1, the present invention does not result in a loss of effective yield even in the region where the raw material conversion rate is high, and it is a highly competitive production method, particularly in the direct oxidation process.

[0085] Table 2 shows the reaction bath temperature and effective yield at a raw material conversion rate of 98.7%, at which the catalysts of the Examples and Comparative Examples showed the highest yield. As is clear from Table 2, the production method of the present invention has a high effective yield even in a range where the raw material conversion rate is not high. Furthermore, Examples 1, 2, 3, 4, and 5 in Table 1 showed effective yields equal to or higher than that of Comparative Example 1 listed in Table 2, even at raw material conversion rates of 99.4% or more, confirming that these catalysts are particularly highly competitive.

[0086] [Table 2] [Industrial Applicability]

[0087] By using the production method of the present invention, when unsaturated aldehyde compounds and unsaturated carboxylic acid compounds are oxidatively produced, high yields can be obtained even in the region of high raw material conversion. Furthermore, by using the production method of the present invention, the yield is improved and the amount of by-products that cause reactor clogging is expected to decrease, making it possible to operate a gas-phase catalytic oxidation process stably and at low cost. Furthermore, the amount of catalytically active components at the inlet side of the reaction tube is increased, making long-term operation possible.

Claims

1. 1. A method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid, comprising using a fixed-bed multi-tubular reactor and providing a plurality of catalyst layers which are separated into n (n is 2 or more) layers in the gas flow direction of the reaction tube, A method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid, wherein the ratio (A1 / A2) of the catalytically active component density (A1) from the raw material gas inlet to half of the total packing length to the catalytically active component density (A2) from half of the total packing length to the raw material gas outlet is 1.10 to 2.

0.

2. 2. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 1, wherein the ratio (R1 / R2) of the average catalyst particle diameter (R1) from the raw material gas inlet to the center of the entire packed length to the average catalyst particle diameter (R2) from the center of the entire packed length to the raw material gas outlet is 0.45 to 0.

95.

3. 3. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 1, wherein a catalyst having a composition represented by the following formula (1) is used as a catalyst in a first layer of the reaction tube: [Formula 1] Mo ａ１ Bi ｂ１ Ni ｃ１ Co ｄ１ Fe ｅ１ X ｆ１ Y ｇ１ Z ｈ１ O ｉ１ ・・・(1) (In the formula, Mo, Bi, Ni, Co, and Fe represent molybdenum, bismuth, nickel, cobalt, and iron, respectively; X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium, and titanium; Y represents at least one element selected from sodium, potassium, cesium, rubidium, and thallium; Z represents an element belonging to Groups 1 to 16 of the periodic table; and and Y, and a1, b1, c1, d1, e1, f1, g1, h1, and i1 represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, X, Y, Z, and oxygen, respectively, and when a1 = 12, 0 < b1 ≤ 7.0, 0 ≤ c1 ≤ 10.0, 0 ≤ d1 ≤ 10.0, 0 < e1 < 5.0, 0 ≤ f1 ≤ 2.0, 0 ≤ g1 ≤ 3.0, 0 ≤ h1 ≤ 5.0, and i1 = a value determined by the oxidation state of each element.

4. 4. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 1, wherein a catalyst having an average particle size of 2.0 mm or more and 4.0 mm or less is used as a catalyst in a first layer of the reaction tube.

5. 5. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 3 or 4, wherein in the formula (1), 0<e1≦1.

7.

6. 6. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 3, wherein b1 satisfies the formula (1), 1.7<b1≦7.

0.

7. 7. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 3, wherein c1 satisfies the formula (1), 1.0≦c1≦10.

0.

8. 8. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 3, wherein, in the formula (1), Y is cesium, and 0.16≦g1≦3.

0.

9. The A1 is 0.30 g / cm ３ 1.0g / cm or more ３ The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of claims 1 to 8, wherein the unsaturated aldehyde and / or the unsaturated carboxylic acid is:

10. 10. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 1, wherein a catalyst supported on an inert carrier at a loading rate of more than 40% is used as a catalyst in a first layer of the reaction tube.

11. The method for producing an unsaturated aldehyde compound and / or an unsaturated carboxylic acid compound according to any one of claims 1 to 10, wherein the raw material conversion rate is 99.0% or more.

12. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to any one of claims 1 to 11, wherein R1 is 2.0 mm or more and 4.49 mm or less.

13. The ratio of the packing length of the first layer of catalyst to the total packing length (x １ 13. The method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid according to claim 1, wherein the ratio of the total amount of the unsaturated aldehyde and / or the unsaturated carboxylic acid to the total amount of the unsaturated aldehyde and / or the unsaturated carboxylic acid is 10% or more and 90% or less.

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