Catalyst for producing unsaturated carboxylic acid and method for producing unsaturated carboxylic acid

Abstract

The present disclosure relates to a catalyst for producing an unsaturated carboxylic acid, in which a catalyst active component has a composition represented by formula (1), and the half-width of a peak at 22.2 DEG + / -0.3 DEG in an X-ray diffraction pattern obtained using a CuK [alpha] ray as an X-ray source is 0.65-1.60 DEG (inclusive). (Mo) 12 (V) a (W) b (Cu) c (Sb) d (X) e (Y) f (Z) g (O) h (1).

Description

Technical Field

[0001] This invention relates to a catalyst for producing unsaturated carboxylic acids in high yield by gas-phase catalytic oxidation of unsaturated aldehydes in the presence of molecular oxygen or a gas containing molecular oxygen, a method for producing the same, and a method for producing unsaturated carboxylic acids using the catalyst. Background Technology

[0002] Acrylic acid is becoming increasingly important as a raw material for water-absorbing resins and adhesives. Therefore, in recent years, there has been a demand for improved catalysts used in the gas-phase catalytic oxidation reaction of acrolein to produce acrylic acid. Consequently, various companies have made improvements to catalysts that can produce acrylic acid in high yields and with long-term stability, and the following solutions have been proposed.

[0003] Patent documents 1 through 4 disclose improvements to catalyst composition, focusing on the X-ray diffraction peaks of the active components. These catalysts are proposed as catalysts achieving high activity and high yield. Furthermore, patent documents 5 and 6 illustrate improvement strategies aimed at enhancing mechanical strength, achieving improved catalyst performance by preventing pulverization during filling. In patent document 7, long-term stability of the catalyst reaction is improved by adjusting the standard deviation of the catalyst particle size to a specific range. Patent document 8 proposes a method for manufacturing a catalyst that combines high catalyst performance and mechanical strength by controlling the relative centrifugal acceleration during rotary granulation. Patent document 9 proposes a method for manufacturing a high-yield catalyst by controlling the density of the catalyst pellet and the surface roughness of the catalyst. Patent document 10 proposes a manufacturing method that obtains high activity and selectivity by controlling the crystal size of the nanocrystalline molybdenum mixed oxide within a specific range.

[0004] However, improving catalyst activity is particularly important in the production of unsaturated carboxylic acids. This not only contributes to increased yield but is also crucial from the perspective of catalyst lifetime. For example, in plants using catalysts, if the reaction bath temperature decreases at the initial stage of the reaction due to increased catalyst activity, not only are the energy costs for heating reduced, but thermal degradation of the catalyst is also mitigated. Therefore, from a long-term perspective, performance degradation is minimal, enabling long-term stable operation and high yields.

[0005] For the reasons mentioned above, there is a need for highly active catalysts and their manufacturing methods.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 8-299797

[0009] Patent Document 2: Japanese Patent Application Publication No. 2003-251184

[0010] Patent Document 3: Japanese Patent Application Publication No. 2015-120133

[0011] Patent Document 4: Japanese Patent Application Publication No. 2018-43197

[0012] Patent Document 5: Japanese Patent Application Publication No. 2001-79408

[0013] Patent Document 6: International Publication No. 2012 / 073584

[0014] Patent Document 7: Japanese Patent Application Publication No. 2009-214105

[0015] Patent Document 8: Japanese Patent Application Publication No. 2015-96497

[0016] Patent Document 9: International Publication No. 2020 / 196150

[0017] Patent Document 10: Japanese Patent Publication No. 2011-516378 Summary of the Invention

[0018] The problem that the invention aims to solve

[0019] In view of the above situation, the object of the present invention is to improve the catalytic activity of a catalyst for producing unsaturated carboxylic acids by gas-phase catalytic oxidation reaction using unsaturated aldehydes as raw materials.

[0020] means for solving problems

[0021] The inventors of this application conducted in-depth research on the aforementioned status quo and issues, and found that specific parameters in the X-ray diffraction pattern help to improve activity, thus completing the invention of this application.

[0022] That is, the present invention relates to the following 1) to 6).

[0023] 1) A catalyst for the production of unsaturated carboxylic acids, wherein the catalyst active component of the catalyst for the production of unsaturated carboxylic acids has the composition shown in formula (1), and the half-width of the peak at 22.2°±0.3° in the X-ray diffraction pattern obtained by using CuKα rays as an X-ray source is 0.65° or more and 1.60° or less.

[0024] (Mo) 12 (V) a (W) b (Cu) c (Sb) d (X) e (Y)f (Z) g (O) h (1)

[0025] (In formula (1), Mo, V, W, Cu, Sb, and O represent molybdenum, vanadium, tungsten, copper, antimony, and oxygen, respectively; X represents at least one element selected from the group consisting of alkali metals and thallium; Y represents at least one element selected from the group consisting of magnesium, calcium, strontium, barium, and zinc; and Z represents at least one element selected from the group consisting of niobium, cerium, tin, chromium, manganese, iron, cobalt, samarium, germanium, titanium, and arsenic. Additionally, a, b, c, d, e, f, g, and h represent the atomic ratios of each element, with a ratio of 12 for molybdenum atoms, 0 < a ≤ 10.0, 0 ≤ b ≤ 10.0, 0 < c ≤ 6.0, 0 ≤ d ≤ 10.0, 0 ≤ e ≤ 0.50, 0 ≤ f ≤ 1.0, and 0 ≤ g < 6.0. Furthermore, h represents the number of oxygen atoms required to satisfy the above-mentioned valence values.)

[0026] 2) The catalyst for the manufacture of unsaturated carboxylic acids according to 1) above, wherein in the above formula (1), 1.0≤a≤5.0, 0.50≤b≤3.0, 0.50≤c≤3.0, and 0<d≤2.0.

[0027] 3) The catalyst for manufacturing unsaturated carboxylic acids according to 1) or 2) above, wherein the catalyst for manufacturing unsaturated carboxylic acids is a catalyst on which the active catalytic component is supported on an inert support.

[0028] 4) The catalyst for the manufacture of unsaturated carboxylic acids according to 3) above, wherein the inert support is silicon dioxide, alumina, or a combination of silicon dioxide and alumina.

[0029] 5) A method for producing an unsaturated carboxylic acid, wherein the method for producing the unsaturated carboxylic acid uses any one of the catalysts for producing unsaturated carboxylic acids described in any one of 1) to 4).

[0030] 6) A method for producing an unsaturated carboxylic acid, wherein the method for producing the unsaturated carboxylic acid uses a reaction tube in which two or more catalysts for producing the unsaturated carboxylic acid as described in any one of 1) to 4) above are filled in multiple layers.

[0031] Invention Effects

[0032] According to the present invention, when producing unsaturated carboxylic acids, i.e. (meth)acrylic acid, by gas-phase catalytic oxidation using unsaturated aldehydes, preferably (meth)acrylaldehyde, as raw materials, high catalyst activity can be maintained. Attached Figure Description

[0033] Figure 1 This is a graph showing the XRD pattern of the active component of catalyst 1 manufactured in Example 1. Detailed Implementation

[0034] [Half-width at half maximum (FWHM) of the peak at 22.2° ± 0.3°]

[0035] The catalyst of the present invention has a half-width at half-maximum of 0.65° and less than 1.60° in the X-ray diffraction (XRD) pattern of the peak at 22.2° ± 0.3° obtained by using CuKα rays as an X-ray source.

[0036] In this specification, half-maximum width at half maximum (HWHM) refers to the width at half maximum, which is the width of the portion of the peak at half the intensity of the fitted quadratic function described later. The detailed effect of the HWHM of the 22.2°±0.3° peak in the X-ray diffraction pattern on activity is not yet clear, but it is believed that a specific crystal structure induces the oxidation reaction of (meth)acrylaldehyde because the HWHM of the 22.2°±0.3° peak is clearly correlated with catalyst activity.

[0037] The active component of the catalyst for the production of (meth)acrylic acid of the present invention is mostly amorphous, but the presence of some crystalline components is considered to exhibit high catalytic activity. When crystals with a diffraction plane at 22.2°±0.3° are grown, the full width at half maximum (FWHM) of the peak at 22.2°±0.3° in the X-ray diffraction pattern decreases. It is believed that the oxidation reaction of (meth)acrylaldehyde occurs within the crystal structure, and that the greater the crystal growth, the more reaction sites are created within the crystal structure, thus increasing the catalyst activity. However, it is also believed that when the crystal becomes too large, physical resistance is generated, making it difficult for (meth)acrylaldehyde, as a raw material, to pass through the interior of the crystal structure, thus reducing the activity.

[0038] Furthermore, the full width at half maximum (FWHM) of the peak at 22.2° ± 0.3° is a value that increases / decreases depending on the number of crystals. When the proportion of amorphous components in the active ingredient decreases and the number of crystals increases, the diffraction plane increases, thus the FWHM decreases, the highly active components increase, and therefore the activity increases.

[0039] Furthermore, the full width at half maximum (FWHM) of the peak at 22.2° ± 0.3° is a value that increases / decreases depending on the distortion of the crystal structure. Generally, catalytic reactions proceed more readily in regions with structural defects. In catalysts used in the manufacture of (meth)acrylic acid, catalysts with a certain degree of structural defects are considered to be highly active. When structural defects are present, the crystal structure is distorted, and the FWHM of the peak at 22.2° ± 0.3° in the X-ray diffraction pattern becomes a large value.

[0040] In summary, the inventors of this invention believe that a catalyst with a certain degree of crystal growth and structural distortion within a certain range and a large number of such crystals is preferred as a catalyst for the manufacture of (meth)acrylic acid. It was found that this can be achieved by adjusting the full width at half maximum (FWHM) of the peak at 22.2°±0.3° in the X-ray diffraction pattern to 0.65° or more and 1.60° or less.

[0041] In this invention, the half-width at half-maximum (WWHM) is 0.65° or more and 1.60° or less. Further preferred values ​​for the lower limit are, in order, 0.70°, 0.75°, 0.80°, 0.85°, 0.88°, 0.90°, 0.92°, 0.94°, and 0.96°, with 0.98° being particularly preferred. Similarly, preferred values ​​for the upper limit are, in order, 1.55°, 1.50°, 1.47°, 1.45°, 1.40°, 1.35°, and 1.33°, with 1.31° being particularly preferred. Therefore, the half-peak width of the peak at 22.2°±0.3° is preferably 0.70° or more and 1.60° or less, more preferably 0.75° or more and 1.60° or less, more preferably 0.80° or more and 1.60° or less, more preferably 0.85° or more and 1.55° or less, more preferably 0.88° or more and 1.50° or less, more preferably 0.90° or more and 1.47° or less, more preferably 0.92° or more and 1.45° or less, more preferably 0.94° or more and 1.40° or less, more preferably 0.96° or more and 1.35° or less, and most preferably 0.98° or more and 1.31° or less. The half-width of the peak at 22.2°±0.3° can be greater than 0.65° and less than 1.47°, greater than 0.65° and less than 1.45°, greater than 0.65° and less than 1.40°, greater than 0.85° and less than 1.60°, greater than 0.88° and less than 1.60°, or greater than 0.90° and less than 1.60°.

[0042] It should be noted that, as a method for measuring the X-ray diffraction angle (2θ), for example, the UltimaIV manufactured by Rigaku Corporation can be used to measure the X-ray diffraction angle (2θ) under the following conditions: the X-ray is CuKα ray (λ=0.154nm), the output power is 40kV, 30mA, the measurement range is 5° to 60°, and the measurement speed is 3° per minute. However, as long as the measurement principle is not deviated from, it is not limited to this.

[0043] [Method for calculating the half-peak width of a peak at 22.2°±0.3°]

[0044] When calculating the full width at half maximum (FWHM), data without baseline smoothing or other processing can be used, and OriginPro (manufactured by LightStone) can be used as the analysis software. As an analytical method, the lines passing through the minimum values ​​of 2θ = 16.0°–18.0° and 2θ = 39.0°–42.0° in the X-ray diffraction pattern are used as the baseline. A quadratic function is fitted to the peaks above the baseline, and the full width at half maximum (FWHM) of the fitted quadratic function with vertices within the range of 2θ = 22.2° ± 0.3° is taken as the FWHM of the peak at 2θ = 22.2° ± 0.3° in the X-ray diffraction pattern.

[0045] [Half-width of the peak at 8.3°±0.5°]

[0046] From the viewpoint of catalytic activity, the catalyst of the present invention further preferably has a half-width at half-maximum (WHM) of the peak at 8.3°±0.5° greater than 0 and less than or equal to 2.82°. As an upper limit for the WHM of the peak at 8.3°±0.5°, further preferably 2.75°, 2.70°, 2.65°, 2.60°, 2.55°, 2.50°, 2.45°, and 2.40°, and particularly preferably 2.37°. Similarly, as a lower limit, further preferably 1.00°, 1.50°, 2.00°, 2.10°, and 2.20°, and particularly preferably 2.30°. Therefore, the half-peak width of the peak at 8.3°±0.5° is more preferably greater than 0 and less than or equal to 2.75°, more preferably greater than 0 and less than or equal to 2.70°, more preferably greater than 0 and less than or equal to 2.65°, more preferably 1.00° or more and 2.60° or less, more preferably 1.50° or more and 2.55° or less, more preferably 2.00° or more and 2.50° or less, more preferably 2.10° or more and 2.45° or less, more preferably 2.20° or more and 2.40° or less, and most preferably 2.30° or more and 2.37° or less.

[0047] [Calculation method for the half-peak width of a peak of 8.3°±0.5°]

[0048] Except for reading the half-peak width of the quadratic function with a vertex in the range of 2θ = 8.3° ± 0.5° in the fitted quadratic function as the half-peak width of the peak, the calculation method is the same as that for the peak at 22.2° ± 0.3°.

[0049] [Half-width of the peak at 26.7°±0.3°]

[0050] From the viewpoint of catalytic activity, the catalyst of the present invention is further preferably characterized by a half-width at half-maximum (WHM) of 4.66° or more and 7.40° or less for the peak at 26.7° ± 0.3°. As an upper limit for the WHM of the peak at 26.7° ± 0.3°, further preferably values ​​are 7.30°, 7.25°, 7.20°, 7.00°, 6.90°, 6.80°, 6.70°, 6.60°, 6.50°, 6.40°, 6.30°, 6.20°, 6.15°, and 6.10°, with a particularly preferred value of 6.05°. Furthermore, similarly, as a lower limit, the following values ​​are further preferred in sequence: 4.80°, 5.00°, 5.05°, 5.10°, 5.20°, 5.30°, 5.40°, 5.45°, 5.50°, 5.60°, 5.70°, 5.80°, and 5.90°, with 5.95° being particularly preferred. Therefore, the half-width at half-maximum (WHM) of the 26.7°±0.3° peak is more preferably 4.66° or more and 7.30° or less, more preferably 4.66° or more and 7.25° or less, more preferably 4.80° or more and 7.20° or less, more preferably 5.00° or more and 7.00° or less, more preferably 5.10° or more and 6.90° or less, more preferably 5.20° or more and 6.80° or less, and more preferably 5.30° or more and 6.70° or less. More preferably, the angle is 5.40° or higher and 6.60° or lower; more preferably, the angle is 5.45° or higher and 6.50° or lower; more preferably, the angle is 5.50° or higher and 6.40° or lower; more preferably, the angle is 5.60° or higher and 6.30° or lower; more preferably, the angle is 5.70° or higher and 6.20° or lower; more preferably, the angle is 5.80° or higher and 6.15° or lower; more preferably, the angle is 5.90° or higher and 6.10° or lower; and most preferably, the angle is 5.95° or higher and 6.05° or lower.

[0051] [Method for calculating the half-peak width of a peak at 26.7°±0.3°]

[0052] Except for reading the half-peak width of the quadratic function with a vertex in the range of 2θ = 26.7° ± 0.3° in the fitted quadratic function as the half-peak width of the peak, the calculation method is the same as that for the peak at 22.2° ± 0.3°.

[0053] [Half-width of the peak at 45.4°±0.3°]

[0054] From the viewpoint of catalytic activity, the catalyst of the present invention is further preferably characterized by a half-maximum width (WHM) of 0.64° or more and 1.03° or less for the peak at 45.4° ± 0.3°. As an upper limit for the WHM of the peak at 45.4° ± 0.3°, it is further preferably 1.00°, 0.99°, or 0.98°, and particularly preferably 0.97°. Similarly, as a lower limit, it is further preferably 0.65°, 0.67°, 0.70°, 0.75°, 0.80°, 0.85°, or 0.90°, and particularly preferably 0.95°. Therefore, the half-peak width of the peak at 45.4°±0.3° is more preferably 0.65° or more and 1.03° or less, more preferably 0.67° or more and 1.03° or less, more preferably 0.70° or more and 1.03° or less, more preferably 0.75° or more and 1.03° or less, more preferably 0.80° or more and 1.00° or less, more preferably 0.85° or more and 0.99° or less, more preferably 0.90° or more and 0.98° or less, and most preferably 0.95° or more and 0.97° or less.

[0055] [Method for calculating the half-peak width of a peak at 45.4°±0.3°]

[0056] Except for reading the half-peak width of the quadratic function with a vertex in the range of 2θ = 45.4° ± 0.3° in the fitted quadratic function as the half-peak width of the peak, the calculation method is the same as that for the peak at 22.2° ± 0.3°.

[0057] [Catalyst Composition]

[0058] The catalyst of the present invention has the composition shown in formula (1).

[0059] [Equation (1)]

[0060] (Mo) 12 (V) a (W) b (Cu) c (Sb) d (X) e (Y) f (Z) g (O) h (1)

[0061] In formula (1), Mo, V, W, Cu, Sb and O represent molybdenum, vanadium, tungsten, copper, antimony and oxygen, respectively; X represents at least one element selected from the group consisting of alkali metals and thallium; Y represents at least one element selected from the group consisting of magnesium, calcium, strontium, barium and zinc; and Z represents at least one element selected from the group consisting of bismuth, tellurium, silver, selenium, silicon, aluminum, boron, niobium, cerium, tin, chromium, manganese, iron, cobalt, nickel, samarium, germanium, zirconium, titanium, chromium, tantalum, lead, indium and sulfur. It is at least one element in the group consisting of palladium, gallium, lanthanum, and arsenic. Furthermore, a, b, c, d, e, f, g, and h represent the atomic ratios of each element relative to molybdenum atoms, where 0 < a ≤ 10.0, 0 ≤ b ≤ 10.0, 0 < c ≤ 6.0, 0 ≤ d ≤ 10.0, 0 ≤ e ≤ 0.50, 0 ≤ f ≤ 1.0, and 0 ≤ g < 6.0. Additionally, h represents the number of oxygen atoms required to satisfy the above-mentioned valence requirements.

[0062] In the above formula (1), the preferred ranges of a to g are as follows.

[0063] The lower limit of 'a' is preferably 0.20, 0.50, 0.80, 1.0, 1.5, 2.0, 2.2, 2.4, with the most preferred value being 2.6. The upper limit of 'a' is preferably 9.0, 8.0, 7.0, 6.0, 5.0, 4.5, 4.0, 3.5, 3.3, 3.1, with the most preferred value being 2.9. That is, the range of 'a' is preferably 0.20≤a≤9.0, more preferably 0.20≤a≤8.0, more preferably 0.20≤a≤7.0, more preferably 0.50≤a≤6.0, more preferably 0.80≤a≤5.0, more preferably 1.0≤a≤4.5, more preferably 1.5≤a≤4.0, more preferably 2.0≤a≤3.5, more preferably 2.2≤a≤3.3, more preferably 2.4≤a≤3.1, and most preferably 2.6≤a≤2.9.

[0064] The lower limit of b, in the preferred order, is 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, with the most preferred value being 0.70. The upper limit of b, in the preferred order, is 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, 1.3, with the most preferred value being 1.1. That is, the range of b is preferably 0.10≤b≤9.0, more preferably 0.10≤b≤8.0, more preferably 0.10≤b≤7.0, more preferably 0.10≤b≤6.0, more preferably 0.10≤b≤5.0, more preferably 0.10≤b≤4.0, more preferably 0.20≤b≤3.0, more preferably 0.30≤b≤2.5, more preferably 0.40≤b≤2.0, more preferably 0.50≤b≤1.5, more preferably 0.60≤b≤1.3, and most preferably 0.70≤b≤1.1.

[0065] The lower limit of c, in the preferred order, is 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, with the most preferred value being 1.3. The upper limit of c, in the preferred order, is 5.0, 4.0, 3.0, 2.5, 2.0, 1.8, with the most preferred value being 1.6. That is, the range of c is preferably 0.10≤c≤5.0, more preferably 0.20≤c≤5.0, more preferably 0.30≤c≤5.0, more preferably 0.40≤c≤5.0, more preferably 0.50≤c≤5.0, more preferably 0.60≤c≤4.0, more preferably 0.70≤c≤3.0, more preferably 0.80≤c≤2.5, more preferably 0.90≤c≤2.0, more preferably 1.0≤c≤1.8, and most preferably 1.3≤c≤1.6.

[0066] The lower limit of d is preferably 0.11, 0.15, 0.18, 0.20, 0.25, 0.30, 0.35, with the most preferred value being 0.40. The upper limit of d is preferably 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, 1.0, with the most preferred value being 0.70. That is, the range of d is preferably 0.11≤d≤9.0, more preferably 0.11≤d≤8.0, more preferably 0.11≤d≤7.0, more preferably 0.11≤d≤6.0, more preferably 0.11≤d≤5.0, more preferably 0.15≤d≤4.0, more preferably 0.18≤d≤3.0, more preferably 0.20≤d≤2.5, more preferably 0.25≤d≤2.0, more preferably 0.30≤d≤1.5, more preferably 0.35≤d≤1.0, and most preferably 0.40≤d≤0.70.

[0067] The upper limit of e is preferably 0.40, 0.30, 0.20, and 0.10. That is, the range of e is preferably 0≤e≤0.40, 0≤e≤0.30, and 0≤e≤0.20, with the most preferred range being 0≤e≤0.10.

[0068] The upper limit of f, in the preferred order, is 0.80, 0.50, 0.20, 0.15, with the most preferred value being 0.10. That is, the range of f, in the preferred order, is 0≤f≤0.80, 0≤f≤0.50, 0≤f≤0.20, 0≤f≤0.15, with the most preferred range being 0≤f≤0.10.

[0069] The upper limit of g, in the preferred order, is 5.0, 4.0, 3.0, 2.0, and 1.0. That is, the range of g, in the preferred order, is 0≤g≤5.0, 0≤g≤4.0, 0≤g≤3.0, and 0≤g≤2.0, with the most preferred range being 0≤g≤1.0.

[0070] It should be noted that the case where e, f, and g are 0 is a particularly preferred method.

[0071] When the catalyst of the present invention is used in reactions that produce corresponding unsaturated carboxylic acids from unsaturated aldehydes such as acrolein and methacrolein, particularly in reactions that produce acrylic acid by gas-phase catalytic oxidation of acrolein using molecular oxygen or a gas containing molecular oxygen, it is highly effective compared to known methods in achieving increased catalyst activity and reduced pressure differential. Furthermore, in processes involving exothermic partial oxidation reactions, improved stability due to reduced hotspot temperatures is also expected. In addition, the catalyst of the present invention is effective in reducing byproducts that adversely affect the environment and the quality of the final product, such as carbon monoxide (CO), carbon dioxide (CO2), acetaldehyde, acetic acid, and formaldehyde.

[0072] [Methods for manufacturing catalysts, etc.]

[0073] The following are examples of specific steps for obtaining the catalyst of the present invention.

[0074] Process a) Preparation

[0075] Examples of raw materials that constitute the elements of a catalyst include the following.

[0076] When ammonium molybdate is used as the raw material for molybdenum, a high-performance catalyst can be obtained.

[0077] As raw materials for tungsten, vanadium, antimony, copper, and other elements, oxides or ammonium salts, carbonates, sulfates, organic acid salts, hydroxides, metal powders, or mixtures thereof that can be converted into oxides by strong heating can generally be used. The preferred raw materials vary depending on the element, and this also allows adjustment of the full width at half maximum (FWHM) of the 22.2°±0.3° peak in the XRD pattern. For example, in the case of tungsten and vanadium, ammonium salts are preferred, and in the case of copper, sulfates are preferred. In the case of antimony raw materials, compounds with a trivalent antimony valence are preferred, and salts of acetic acid, carbonic acid, tartaric acid, oxalic acid, and other carboxylic acids are particularly preferred. The vanadium, molybdenum, tungsten, and antimony raw materials are mixed in an aqueous solvent at a desired ratio in an aqueous solution at 20°C to 95°C, heated and stirred for about 1 hour, and then, as needed, raw materials of component X, component Y, and component Z are added. Finally, an aqueous solution containing dissolved copper is added. An aqueous solution or slurry containing the catalyst components is obtained, which will be referred to hereafter as the formulation (A). When using metal powder as a raw material, it is preferable to add it at the same time as the antimony raw material. When using copper raw material with a divalent valence as the copper raw material, it is preferable to add it after adding the antimony raw material and the metal powder. When adding divalent copper raw material before antimony raw material and metal powder, low-activity crystals will be formed, resulting in a decrease in catalyst performance.

[0078] Here, the formulation (A) does not necessarily need to contain all the catalyst constituent elements; some elements or amounts may be added in subsequent processes. Furthermore, if the amount of water used to dissolve each component raw material during the preparation of the formulation (A), or if the concentration of the acid in the aqueous solution sufficient to dissolve the raw material (e.g., in the case of adding acids such as sulfuric acid, nitric acid, hydrochloric acid, tartaric acid, or acetic acid for dissolution) is unsuitable, the formulation (A) may sometimes be in the form of a clay-like block, which is not ideal for a catalyst. From the perspective of obtaining an excellent catalyst, an aqueous solution or a slurry is preferred for the resulting formulation (A).

[0079] Process b) Drying

[0080] Next, the prepared liquid (A) obtained above is dried to produce a dried powder. There are no particular limitations on the drying method, as long as it can completely dry the prepared liquid (A), examples include: drum drying, freeze drying, spray drying, evaporative drying, etc. In this invention, spray drying, which can dry a slurry into powder or particles in a short time, is particularly preferred. The drying temperature of the spray dryer varies depending on the slurry concentration, the feed rate, etc., but is generally between 70°C and 150°C at the dryer outlet. Furthermore, drying is preferably carried out in a manner that results in an average particle size of 20 μm to 700 μm for the dried powder obtained at this time. This yields dried powder (B).

[0081] Process c) Pre-calcination

[0082] The obtained dry powder (B) tends to exhibit improved catalyst formability, mechanical strength, and catalyst performance by calcining it at 200°C to 500°C, preferably 300°C to 400°C, under air circulation. The calcination time is preferably 1 hour to 12 hours. This yields a pre-calcined body (C).

[0083] Process d) Crushing

[0084] The resulting pre-calcined body (C) is obtained as a solid (D) formed by the agglomeration of dried powder (B) through pre-calcination. To obtain the pre-calcined powder (E) required in the subsequent forming process, the solid (D) is pulverized. The pulverization method is not particularly limited, and examples include: roller mills, jet mills, hammer mills, ball mills, vibratory mills, etc. The average particle size (median pre-calcined particle size) of the pre-calcined powder (E) obtained at this time is preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less.

[0085] It should be noted that in this application specification, the pulverized pre-calcined powder (E) is described as a catalyst precursor. However, in the stage of pre-calcined body (C), if there is no agglomeration and it can be used even without a pulverization process, the pre-calcined body (C) can also be used as a catalyst precursor.

[0086] Process e) Forming

[0087] There are no particular restrictions on the forming method. When forming into a cylindrical or annular shape, it is preferable to use a tablet forming machine, an extrusion forming machine, or the like. Further preferred is the case of forming into a spherical shape. The pre-calcined powder (E) can be formed into a spherical shape using a forming machine, but it is preferable to load the pre-calcined powder (E) (which may contain forming aids and strength enhancers as needed) onto an inert ceramic or other carrier. Here, as loading methods, rotary granulation, methods using centrifugal flow coating devices, and washing methods are widely known. There are no particular limitations as long as the method can uniformly load the pre-calcined powder (E) onto the carrier. However, considering the catalyst manufacturing efficiency and the performance of the prepared catalyst, the following method is more preferred: In a device with a flat or convex disc at the bottom of a fixed cylindrical container, the disc is rotated at high speed, thereby vigorously stirring the carrier filled into the container by its own rotation and revolution. The pre-calcined powder (E) and, as needed, forming aids and / or strength enhancers and pore-forming agents are added, thereby loading the powder components onto the carrier. Rotary granulation is the most preferred method. It should be noted that a binder is preferably used during loading. Specific examples of binders that can be used include: water, ethanol, methanol, propanol, polyols, polyvinyl alcohol as a polymeric binder, and silica sol aqueous solution as an inorganic binder. Ethanol, methanol, propanol, and polyols are preferred, and glycols such as ethylene glycol and triols such as glycerol are more preferred. By using an appropriate amount of aqueous glycerol solution, the formability becomes good, and a high-performance catalyst with high mechanical strength can be obtained. Specifically, a high-performance catalyst can be obtained especially when using an aqueous solution with a glycerol concentration of 5% by mass or more. The amount of these binders used is usually 2 to 80 parts by mass relative to 100 parts by mass of the pre-calcined powder (E). An inert support of about 2 mm to about 8 mm is usually used, on which the pre-calcined powder (E) is loaded. The loading rate is determined considering the catalyst usage conditions, such as the space velocity of the reactants, the concentration of the reactants, etc., and is usually 20% to 80% by mass. Here, when forming aids, strength enhancers, etc. are present for forming, the loading rate is expressed as in the following formula (4). The formed body (F) is thus obtained.

[0088] Furthermore, the inventors have discovered that the catalyst of this invention sometimes exhibits poor mechanical strength. Therefore, it is preferable to add inert inorganic fibers as strength enhancers during loading and forming. The amount of these fibers used is typically 1 to 30 parts by mass relative to 100 parts by mass of the pre-calcined powder (E).

[0089] [Regarding load]

[0090] Catalysts with particularly good performance are obtained by loading a pre-calcined body (C) obtained by pre-calcining the catalyst active component after preparation, or a pulverized pre-calcined powder (E) obtained by further pulverizing the pre-calcined body (C) onto an inert support.

[0091] As the material for the inert support, known substances such as alumina, silicon dioxide, titanium dioxide, zirconium oxide, niobium oxide, silicon dioxide-alumina, silicon carbide, carbides, and mixtures thereof can be used. There are no particular restrictions on the particle size, water absorption rate, mechanical strength, crystallinity of each crystal phase, and mixing ratio of the inert support; an appropriate range should be selected considering the performance, formability, and production efficiency of the final catalyst. As for the shape of the inert support, spherical shape is preferred, but there are no particular restrictions; granular or cyclic inert supports can be used. The mixing ratio of the support to the pre-calcined powder is usually calculated as the loading rate based on the mass of each raw material fed, using the following formula (4). It should be noted that if the forming aids, strength enhancers, and other additives used remain in the catalyst after formal calcination, they should be included in the total amount (denominator).

[0092] [Equation (4)]

[0093] Loading rate (mass%) = (mass of pre-calcined powder used in forming) / {(mass of pre-calcined powder used in forming) + (mass of carrier used in forming)} × 100 (4)

[0094] The preferred upper limit for the above-mentioned load rate is 80% mass, and the further preferred order is 70% mass, 60% mass, 55% mass, 50% mass, 45% mass, and 40% mass.

[0095] Furthermore, the preferred lower limit is 10% by mass, and the further preferred order is 15% by mass, 18% by mass, and 20% by mass. That is, the load rate is preferably 10% by mass or more and 80% by mass or less, more preferably 10% by mass or more and 70% by mass or less, more preferably 10% by mass or more and 60% by mass or less, more preferably 10% by mass or more and 55% by mass or less, more preferably 15% by mass or more and 50% by mass or less, more preferably 18% by mass or more and 45% by mass or less, and the most preferred range is 20% by mass or more and 40% by mass or less.

[0096] [Regarding Inorganic Fibers]

[0097] For the purpose of improving mechanical strength and the like, the catalyst of the present invention preferably contains inorganic fibers. The material of the inorganic fibers is not particularly limited. For example, glass fibers (glass fibers), ceramic fibers, metal fibers, mineral fibers, carbon fibers, various whiskers, etc. can be used. Among them, glass fibers treated with silane-based chemicals are particularly preferred.

[0098] In addition, the fiber length of the inorganic fibers is not particularly limited as long as it does not hinder the effects of the present invention. The average fiber length is preferably about 1 μm to about 1000 μm, and more preferably about 10 μm to about 500 μm.

[0099] In addition, two or more kinds of the inorganic fibers can be used in combination, which can be two or more kinds of inorganic fibers with different materials, or two inorganic fibers with the same material but different average fiber lengths.

[0100] Process f) Formal Calcination

[0101] The formed body (F) has a tendency to have catalyst activity and an increased effective yield by calcining at a temperature of 100°C to 450°C for about 1 hour to about 12 hours. The calcination temperature is preferably 27°C or higher and 420°C or lower, and more preferably 350°C or higher and 400°C or lower. As the flowing gas, air is simple and is preferred. However, in addition, nitrogen, carbon dioxide, argon, helium, nitrogen oxide gas, ammonia gas, hydrogen, and mixtures thereof used as inert gases can also be used. The catalyst (G) is obtained in this way.

[0102] [Method for Adjusting the Half-Peak Width of the Peak at 22.2°±0.3°]

[0103] The value of the above half-peak width can be adjusted by changing the types and ratios of the raw materials used in the above step a), the spray drying conditions in step b), the calcination temperature, time and atmosphere in step c), the pulverization method and the median particle size after pulverization in step d), the relative centrifugal acceleration, the loading rate, the type of binder, the addition position of the binder, etc. in step e). However, it is difficult to change it significantly when changing the conditions individually, and it can be achieved by optimizing two or more conditions. Some examples are illustrated below.

[0104] <Types and Ratios of Raw Materials Used in Step a)>

[0105] The full width at half maximum (FWHM) of the peak at 22.2° ± 0.3° in the XRD pattern can be adjusted by changing the types of raw materials used. In particular, the compound that can act as a reducing agent can be changed. When a trivalent antimony compound is used, the FWHM becomes larger. When metal powders such as molybdenum and copper with an oxidation number of 0, or organic substances such as oxalic acid and citric acid are used, the FWHM becomes smaller. In addition, by adjusting the composition ratio of metal elements, the control of the FWHM can also be carried out. The catalyst of the present invention has molybdenum and vanadium as the basic framework. The more elements other than these increase, the more the crystal structure is distorted, so there is a tendency for the FWHM to become larger. In particular, tungsten and antimony atoms strongly impart distortion to the crystal structure. Therefore, the more these raw materials are used, the easier it is for the FWHM to become larger. On the contrary, when a large amount of copper raw material is used, the FWHM is likely to become smaller. From this point of view, for example, the atomic ratio d of antimony to 12 molybdenum atoms in formula (1) can be 0 < d < 1.0, can also be 0.25 ≤ d ≤ 0.75, and can also be 0.25 ≤ d ≤ 0.50.

[0106] <c) Calcination temperature, time and atmosphere in the process>

[0107] The calcination temperature is preferably 200°C to 500°C as described above. When the calcination temperature increases, the growth of crystals is promoted, so there is a tendency for the FWHM to become smaller. However, when the temperature is too high or the time is too long, the crystals undergo thermal decomposition and the quantity decreases, so the FWHM becomes larger. Therefore, from the viewpoint of adjusting the FWHM, it is preferably less than 400°C and less than 6 hours.

[0108] The gas atmosphere during calcination can be air. However, when oxygen molecules are present, it will hinder crystal growth. Therefore, when calcination is carried out in an inert gas atmosphere such as nitrogen or argon, or a reducing gas atmosphere such as hydrogen or ammonia, the FWHM can be reduced.

[0109] <d) Grinding method, median particle size and centrifugal acceleration in the process>

[0110] The FWHM can also be controlled by the method of step d). When using a ball mill, it is easy to adjust the FWHM. The FWHM can also be adjusted by adjusting the median particle size of the pre-calcined powder to be below a certain value. The median particle size of the pre-calcined powder is preferably 50 μm or less. In addition, the FWHM can also be adjusted by changing the relative centrifugal acceleration in the case of rotary granulation in step e) according to the median particle size of the pre-calcined powder. When the median particle size is less than 30 μm, the relative centrifugal acceleration can be set to 10 G or more.

[0111] [Use of the catalyst]

[0112] In the method for producing unsaturated carboxylic acids such as acrylic acid using the catalyst of the present invention, the flow method of the raw material gas can be a conventional single-flow method or a recirculation method, and can be carried out under normal operating conditions without particular limitation. For example, a mixed gas containing 1% to 10% (ideally 4% to 9% by volume) of the starting material as an ideal gas, 3% to 20% (preferably 4% to 18% by volume) of molecular oxygen, 0% to 60% (preferably 4% to 50% by volume) of water vapor, and 20% to 80% (preferably 30% to 75% by volume) of inactive gases such as carbon dioxide and nitrogen is subjected to a pressure of 200°C to 450°C and atmospheric pressure to 10 atmospheres for 300 hours. -1 ~5000 hours -1 The space velocity is introduced onto the catalyst of the present invention, which is filled in the reaction tube, and the reaction takes place.

[0113] Furthermore, in the above-described method for producing unsaturated carboxylic acids, a single catalyst can be used, or multiple layers of different types of catalysts can be used depending on the conditions of use. Specifically, a catalyst layer formed by dividing the feed gas flow direction along the reaction tube into n segments can be constructed, and the various catalysts can be arranged such that their activity increases from the feed gas inlet to the outlet in the feed gas flow direction. The number of segments n is not particularly limited, typically 2 to 5, preferably 2 to 3. The different types of catalysts refer not only to different catalyst compositions, but also to different loading rates on the inert support and different dilution rates. Alternatively, a catalyst whose activity has been improved by adjusting the half-peak width of this invention can be placed on the feed gas outlet side, while a catalyst with relatively lower activity can be placed on the feed gas inlet side.

[0114] Example

[0115] The present invention will be described in more detail below through examples. It should be noted that, in the examples, the raw material conversion rate, yield, and selectivity are calculated according to the following formulas.

[0116] Raw material conversion rate (%) = (number of moles of acrolein that reacted) / (number of moles of acrolein supplied) × 100

[0117] Yield (%) = (moles of acrylic acid produced) / (moles of acrolein supplied) × 100

[0118] Selectivity (%) = (moles of acrylic acid produced) / (moles of acrolein that reacted) × 100

[0119] The following examples illustrate embodiments, but the present invention is not limited to these embodiments as long as it does not depart from its spirit. It should be noted that the 2θ = 22.2° half-width at half-maximum shown in this embodiment was obtained by analyzing data obtained from X-ray diffraction angle (2θ) measurements performed using an OriginPro 2022b manufactured by LightStone Corporation and an UltimaIV manufactured by Rigaku Corporation, under the conditions of CuKα X-rays (λ = 0.154 nm), output power of 40 kV, 30 mA, measurement range of 5° to 60°, and measurement speed of 3° per minute. As an analytical method, as described above, the lines passing through the minimum values ​​of 2θ = 16.0° to 18.0° and 2θ = 39.0° to 42.0° in the X-ray diffraction pattern are used as the baseline. A quadratic function is fitted to the peaks located above the baseline, and the half-width of the fitted quadratic function with vertices in the range of 2θ = 22.2° ± 0.3° is read as the half-width of the peak at 2θ = 22.2° ± 0.3° in the X-ray diffraction pattern.

[0120] [Example 1]

[0121] <Catalyst 1 Manufacturing>

[0122] In relation to Mo 12 The composition is V 2.7 W 0.8 Cu 1.5 Sb 0.50 Ammonium molybdate, ammonium paratungstate, ammonium metavanadate, and antimony acetate were measured and mixed in an aqueous solvent (5.2 times the mass of ammonium molybdate) heated to 95°C. Copper sulfate was then added to obtain a formulation (A). The formulation (A) was dried using spray drying, and the resulting dried powder (B) was pre-calcined at 350°C for 4 hours to obtain a pre-calcined body (C). The pre-calcined body (C) was pulverized using a ball mill to obtain pre-calcined powder (E). 5% by mass of crystalline cellulose and 5% by mass of glass fiber with an average fiber length of 150 μm relative to the pre-calcined powder (E) were added and thoroughly mixed. The mixture was then granulated using a rotary granulator with a 20% by mass glycerol solution as a binder on an inert spherical carrier containing a mixture of silica and alumina at a loading rate of 33% by mass and an average particle size of 5 mm. A rotary granulator was used for granulation at a centrifugal acceleration of 26.0 G. Next, the catalyst was calcined at 390°C for 4 hours to obtain the spherical catalyst 1 of the present invention.

[0123] [Example 2]

[0124] <Catalyst 2 Manufacturing>

[0125] In relation to Mo 12 The composition is V 3.0 W 1.2 Cu 1.5 Sb 0.50 Ammonium molybdate, ammonium paratungstate, ammonium metavanadate, and antimony acetate were measured and mixed in an aqueous solvent (5.2 times the mass of ammonium molybdate) heated to 95°C. Copper sulfate was then added to obtain a formulation (A). The formulation (A) was dried using spray drying, and the resulting dried powder (B) was pre-calcined at 350°C for 4 hours to obtain a pre-calcined body (C). The pre-calcined body (C) was pulverized using a ball mill to obtain pre-calcined powder (E). 5% by mass of crystalline cellulose and 5% by mass of glass fiber with an average fiber length of 150 μm relative to the pre-calcined powder (E) were added and thoroughly mixed. The mixture was then granulated using a rotary granulator with a 20% by mass glycerol solution as a binder on an inert spherical carrier containing a mixture of silica and alumina at a loading rate of 33% by mass and an average particle size of 5 mm. A rotary granulator was used for granulation at a centrifugal acceleration of 26.0 G. Next, the catalyst was calcined at 390°C for 4 hours to obtain the spherical catalyst 2 of the present invention.

[0126] [Example 3]

[0127] <Catalyst 3 Manufacturing>

[0128] In relation to Mo 12 The composition is V 3.0 W 1.2 Cu 1.2 Sb 0.25 Ammonium molybdate, ammonium paratungstate, ammonium metavanadate, powdered copper, and antimony acetate were measured and mixed in an aqueous solvent (5.2 times the mass of ammonium molybdate) heated to 95°C. Copper sulfate was then added to obtain solution (A). Regarding the copper powder, copper (powder) manufactured by Kanto Chemical Co., Ltd. (specification: Grade 1, particle size: 75μm~150μm) was used, with a Cu-Mo ratio. 12The amount of copper sulfate used was 0.25, and the remaining amount was equivalent to 0.95. The prepared solution (A) was dried by spray drying, and the resulting dried powder (B) was pre-calcined at 350°C for 4 hours to obtain a pre-calcined body (C). The pre-calcined body (C) was pulverized using a ball mill to obtain a pre-calcined powder (E). 5% by mass of crystalline cellulose and 5% by mass of glass fiber with an average fiber length of 150 μm relative to the pre-calcined powder (E) were added and thoroughly mixed. Then, the mixture was granulated by rotary granulation using a 20% by mass glycerol solution as a binder on an inert spherical carrier containing a mixture of silica and alumina at a loading rate of 33% by mass and an average particle size of 5 mm. A rotary granulator was used for granulation, with a centrifugal acceleration of 26.0 G. Finally, formal calcination was performed at 390°C for 4 hours to obtain the spherical catalyst 3 of the present invention.

[0129] [Example 4]

[0130] <Catalyst 4 Manufacturing>

[0131] In relation to Mo 12 The composition is V 3.0 W 1.2 Cu 1.2 Sb 0.50 Ammonium molybdate, ammonium paratungstate, ammonium metavanadate, and antimony acetate were measured and mixed in an aqueous solvent (5.2 times the mass of ammonium molybdate) heated to 95°C. Copper sulfate was then added to obtain a formulation (A). The formulation (A) was dried using spray drying, and the resulting dried powder (B) was pre-calcined at 350°C for 4 hours to obtain a pre-calcined body (C). The pre-calcined body (C) was pulverized using a ball mill to obtain pre-calcined powder (E). 5% by mass of crystalline cellulose and 5% by mass of glass fiber with an average fiber length of 150 μm relative to the pre-calcined powder (E) were added and thoroughly mixed. The mixture was then granulated using a rotary granulator with a 20% by mass glycerol solution as a binder on an inert spherical carrier containing a mixture of silica and alumina at a loading rate of 33% by mass and an average particle size of 5 mm. A rotary granulator was used for granulation at a centrifugal acceleration of 26.0 G. Next, the catalyst was calcined at 390°C for 4 hours to obtain the spherical catalyst 4 of the present invention.

[0132] [Comparative Example 1]

[0133] <Catalyst 5 Manufacturing>

[0134] In relation to Mo 12 The composition is V 3.0W 1.2 Cu 1.2 Ammonium molybdate, ammonium paratungstate, ammonium metavanadate, and metallic copper powders were measured and mixed in an aqueous solvent heated to 95°C in an amount 5.2 times the mass of ammonium molybdate. Copper sulfate was then added to obtain a formulation (A). For the metallic copper powder, copper (powder) manufactured by Kanto Chemical Co., Ltd. (specification: Grade 1, particle size: 75μm~150μm) was used, with a Cu to Mo12 molar ratio of 0.50, and the remaining amount (equivalent to 0.70) was copper sulfate. The formulation (A) was dried using a spray drying method, and the resulting dried powder (B) was pre-calcined at 350°C for 4 hours to obtain a pre-calcined body (C). The pre-calcined body (C) was then pulverized using a ball mill to obtain pre-calcined powder (E). 5% by mass of crystalline cellulose and 5% by mass of glass fiber with an average fiber length of 150 μm relative to the pre-calcined powder (E) were added and thoroughly mixed. The mixture was then granulated by rotary granulation using a 20% by mass glycerol solution as a binder on an inert spherical carrier containing a mixture of silica and alumina at a loading rate of 33% by mass and an average particle size of 5 mm. A rotary granulator was used for granulation, with a centrifugal acceleration of 26.0 G. Subsequently, formal calcination was carried out at 390°C for 4 hours to obtain the spherical catalyst 5 of the present invention.

[0135] [Comparative Example 2]

[0136] <Catalyst 6 Manufacturing>

[0137] In relation to Mo 12 The composition is V 3.0 W 1.2 Cu 1.2Ammonium molybdate, ammonium paratungstate, ammonium metavanadate, and metallic molybdenum powders were measured and mixed in an aqueous solvent heated to 95°C in an amount 5.2 times the mass of ammonium molybdate. Copper sulfate was then added to obtain a formulation (A). For the metallic molybdenum powder, SIGMA-ALDRICH manufactured molybdenum (powder, 1μm–5μm, ≥99.9% trace metals basis) was used. The amount used was calculated as follows: 0.50 of the Mo12 molar ratio was metallic molybdenum, and the remaining 11.5 was ammonium molybdate. The formulation (A) was dried using spray drying. The resulting dried powder (B) was pre-calcined at 350°C for 4 hours to obtain a pre-calcined body (C). The pre-calcined body (C) was then pulverized using a ball mill to obtain pre-calcined powder (E). 5% by mass of crystalline cellulose and 5% by mass of glass fiber with an average fiber length of 150 μm relative to the pre-calcined powder (E) were added and thoroughly mixed. The mixture was then rotary granulated using a 20% by mass glycerol solution as a binder on an inert spherical carrier containing a mixture of silica and alumina at a loading rate of 33% by mass and an average particle size of 5 mm. A rotary granulator was used for shaping, with a centrifugal acceleration of 26.0 G. Subsequently, formal calcination was carried out at 390°C for 4 hours to obtain the spherical catalyst 6 of the present invention.

[0138] [Comparative Example 3]

[0139] <Catalyst 7 Manufacturing>

[0140] In relation to Mo 12 The composition is V 3.0 W 1.2 Cu 1.0 Sb 1.0Ammonium molybdate, ammonium paratungstate, ammonium metavanadate, and antimony acetate were measured and mixed in an aqueous solvent (5.2 times the mass of ammonium molybdate) heated to 95°C. Copper sulfate was then added to obtain a formulation (A). The formulation (A) was dried using spray drying, and the resulting dried powder (B) was pre-calcined at 350°C for 4 hours to obtain a pre-calcined body (C). The pre-calcined body (C) was pulverized using a ball mill to obtain pre-calcined powder (E). 5% by mass of crystalline cellulose and 5% by mass of glass fiber with an average fiber length of 150 μm relative to the pre-calcined powder (E) were added and thoroughly mixed. The mixture was then granulated using a rotary granulator with a 20% by mass glycerol solution as a binder on an inert spherical carrier containing a mixture of silica and alumina at a loading rate of 33% by mass and an average particle size of 5 mm. A rotary granulator was used for granulation at a centrifugal acceleration of 26.0 G. Next, the catalyst was calcined at 390°C for 4 hours to obtain the spherical catalyst 7 of the present invention.

[0141] Oxidation reactions were carried out using catalysts 1 through 7. 67.6 ml of catalyst was packed into a reaction tube with an inner diameter of 28.4 mm. A gas with the following composition was introduced into the gas obtained by gas-phase catalytic oxidation of propylene using a molybdenum-bismuth catalyst, with the addition of oxygen and nitrogen. The reaction was carried out at a space velocity (SV; flow rate of feed gas per unit time / apparent volume of packed catalyst) of 1020 / h and a reaction bath temperature of 260°C.

[0142] acrolein 5.9% by volume

[0143] Unreacted propylene + other organic compounds 1.7% by volume

[0144] Oxygen 4.7% by volume

[0145] Steam 17.2% by volume

[0146] 70.5% by volume of inert gas containing nitrogen

[0147] The reaction results obtained through oxidation are shown in Table 1, and the full width at half maximum (FWHM) of each peak in the X-ray diffraction patterns are shown in Tables 2 and 3. It should be noted that Table 3 is for reference only.

[0148] [Table 1]

[0149] [Table 2]

[0150] [Table 3]

[0151] The results in Tables 1 and 2 confirm that the catalyst of the present invention has a high feed conversion rate, i.e., high catalyst activity.

[0152] [Reference Example 3]

[0153] The catalyst described in Example 1 of Patent Document 1 was prepared according to the embodiments described in Patent Document 1. Specifically, ammonium tungstate, ammonium metavanadate, ammonium molybdate, antimony trioxide powder, and copper sulfate were used as raw materials to obtain a catalyst with properties relative to Mo. 12 The composition is V3W 1.2 Cu 1.2 Sb 0.5 The catalyst is a catalyst containing the active catalytic component. The full width at half maximum (FWHM) of the obtained catalyst was measured using the method described in this invention, and the FWHM at 22.2° ± 0.3° in the X-ray diffraction pattern was 0.52. Furthermore, an oxidation reaction was performed using the method described in this invention, resulting in a reaction temperature of 260°C, a feed conversion rate of 19.6%, a selectivity of 96.3%, and a yield of 18.9%.

[0154] This application is based on Japanese Patent Application No. 2023-150163, filed on September 15, 2023, the contents of which are incorporated herein by reference.

[0155] Industrial practicality

[0156] According to the present invention, high catalyst activity can be maintained when producing unsaturated carboxylic acids by gas-phase catalytic oxidation using unsaturated aldehydes as raw materials. Therefore, thermal degradation of the catalyst used in acrylic acid production can be prevented, enabling long-term stable operation of the plant, which is extremely useful.

Claims

1. A catalyst for the production of unsaturated carboxylic acids, wherein, The catalyst active component of the catalyst for the production of unsaturated carboxylic acids has the composition shown in formula (1), and the half-width at half-maximum (WHM) of the peak at 22.2°±0.3° in the X-ray diffraction pattern obtained using CuKα rays as an X-ray source is 0.65° or more and 1.60° or less. (For) 12 (V) a (W) b (Cu) c (Sb) d (X) e (Y) f (Z) g (of) h (1) (In formula (1), Mo, V, W, Cu, Sb and O represent molybdenum, vanadium, tungsten, copper, antimony and oxygen, respectively; X represents at least one element selected from the group consisting of alkali metals and thallium; Y represents at least one element selected from the group consisting of magnesium, calcium, strontium, barium and zinc; Z represents at least one element selected from the group consisting of niobium, cerium, tin, chromium, manganese, iron, cobalt, samarium, germanium, titanium and arsenic; a, b, c, d, e, f, g and h represent the atomic ratios of each element, relative to 12 molybdenum atoms, 0 < a ≤ 10.0, 0 ≤ b ≤ 10.0, 0 < c ≤ 6.0, 0 ≤ d ≤ 10.0, 0 ≤ e ≤ 0.50, 0 ≤ f ≤ 1.0, 0 ≤ g < 6.0; h is the number of oxygen atoms required to satisfy the atomic valence of the above components).

2. The catalyst for the production of unsaturated carboxylic acids according to claim 1, wherein, In the above formula (1), 1.0≤a≤5.0, 0.50≤b≤3.0, 0.50≤c≤3.0, and 0<d≤2.

0.

3. The catalyst for the production of unsaturated carboxylic acids according to claim 1 or 2, wherein, The catalyst for the production of unsaturated carboxylic acids is a catalyst in which the active catalytic component is supported on an inert support.

4. The catalyst for the production of unsaturated carboxylic acids according to claim 3, wherein, The inert carrier is silicon dioxide, aluminum oxide, or a combination of silicon dioxide and aluminum oxide.

5. A method for manufacturing an unsaturated carboxylic acid, wherein, The method for producing the unsaturated carboxylic acid uses the catalyst for producing unsaturated carboxylic acids as described in claim 1 or 2.

6. A method for producing an unsaturated carboxylic acid, wherein, The method for producing the unsaturated carboxylic acid uses a reaction tube in which two or more catalysts for producing the unsaturated carboxylic acid as described in claim 1 or 2 are filled in multiple layers.

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