Catalyst for producing acrolein and / or acrylic acid, method for producing same, and method for producing acrolein and / or acrylic acid

Abstract

The present disclosure provides a catalyst with which it is possible to improve the yield of acrolein and / or acrylic acid. According to the present disclosure, there is provided a catalyst for producing acrolein and / or acrylic acid by catalytic vapor phase oxidation of propylene in the presence of molecular oxygen or a molecular-oxygen-containing gas, the catalyst containing Fe2MoxOy composite oxide (x = 1.0-5.0, y = 5.0-20.0), and being such that, in X-ray diffraction analysis using ZnO as an internal standard substance, the ratio of the intensity of the maximum peak among the peaks belonging to Fe2MoxOy at 2θ = 19.5-22.5° to the intensity of the maximum peak among the peaks attributed to ZnO at 2θ = 34.2-34.6° is greater than 0.23.

Description

Catalyst for producing acrolein and / or acrylic acid, its production method, and method for producing acrolein and / or acrylic acid

[0001] The present invention relates to a catalyst for producing acrolein and / or acrylic acid, a method for producing the same, and a method for producing acrolein and / or acrylic acid. In particular, the present invention relates to an oxidation catalyst suitable for producing acrolein and / or acrylic acid by catalytic gas-phase oxidation of propylene with molecular oxygen, and a method for producing the same.

[0002] Acrylic acid is an important industrial raw material for various synthetic resins, paints, and plasticizers, and in recent years has become increasingly important as a raw material for acrylic esters and water-absorbent resins. Furthermore, acrylic acid and its derivatives and (co)polymers are used in numerous industrial applications, including paints, coatings, adhesives, fibers, and inks.

[0003] The most commonly used method for producing acrylic acid is a two-stage gas-phase oxidation reaction in which propylene is catalytically oxidized in a gas phase to obtain mainly acrolein, and the acrolein obtained is then catalytically oxidized in a gas phase to obtain acrylic acid. In such a method for producing acrylic acid by catalytically oxidizing propylene in a gas phase in the presence of a molecular oxygen-containing gas, an oxidation catalyst containing a predetermined composite metal oxide is used to produce acrolein and / or acrylic acid from propylene.

[0004] For example, International Publication No. 2010 / 038677 (corresponding to the specification of U.S. Patent Application Publication No. 2011 / 0112325) discloses an oxidation catalyst for producing acrolein and / or acrylic acid, which contains molybdenum, bismuth, and cobalt as catalytically active components, and has a crystallinity T of 4% or more and 18% or less within a diffraction angle (2θ) range of 5° or more and 90° or less, as measured by X-ray diffraction analysis using Cu-Kα radiation of the catalytically active components.

[0005] The oxidation catalysts described in the above documents can exhibit high performance as practical catalysts for producing acrolein from propylene. Meanwhile, acrylic acid is currently mass-produced worldwide at a scale of several million tons per year, and demand for it is growing. Furthermore, due to the recent rise in raw material prices and utility costs, even a 0.1 mol% improvement in the yield of acrylic acid on an industrial scale would be economically significant. Therefore, there is a strong demand for further improvements in the yields of acrolein and acrylic acid.

[0006] Therefore, an object of the present invention is to provide a catalyst capable of improving the yield of acrolein and / or acrylic acid. Another object of the present invention is to provide a method for producing such a catalyst.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by using a catalyst containing a composite oxide containing Fe and Mo and having a specific crystal structure in a predetermined ratio, thereby completing the present invention.

[0008] That is, the above object is to provide a catalyst for producing acrolein and / or acrylic acid by catalytic gas phase oxidation of propylene in the presence of molecular oxygen or a molecular oxygen-containing gas, the catalyst comprising Fe ２ Mo ｘ O ｙ The present invention relates to a composite oxide, wherein x is 1.0 to 5.0, y is 5.0 to 20.0, and in an X-ray diffraction analysis using ZnO as an internal standard, the ratio of the intensity of the maximum peak among peaks attributed to ZnO at a diffraction angle (2θ) of 34.2 to 34.6° to the intensity of Fe at 2θ of 19.5 to 22.5° ２ Mo ｘ O ｙ This can be achieved by a catalyst for producing acrolein and / or acrylic acid, in which the ratio of the maximum peak intensity among peaks attributed to the composite oxide exceeds 0.23.

[0009] One aspect of the present invention is a catalyst for producing acrolein and / or acrylic acid by catalytic gas phase oxidation of propylene in the presence of molecular oxygen or a molecular oxygen-containing gas, the catalyst comprising: ２ Moｘ O ｙ The present invention relates to a composite oxide, wherein x is 1.0 to 5.0, y is 5.0 to 20.0, and in an X-ray diffraction analysis using ZnO as an internal standard, the ratio of the intensity of the maximum peak among peaks attributed to ZnO at a diffraction angle (2θ) of 34.2 to 34.6° to the intensity of Fe at 2θ of 19.5 to 22.5° ２ Mo ｘ O ｙ The catalyst for producing acrolein and / or acrylic acid has a ratio of the maximum peak intensity among peaks attributable to the composite oxide of more than 0.23. The catalyst of the present invention can improve the yield of acrolein and / or acrylic acid.

[0010] In this specification, the "catalyst for producing acrolein and / or acrylic acid" is also referred to simply as the "catalyst" or the "catalyst according to the present invention." ２ Mo ｘ O ｙ The composite oxide (where x is 1.0 to 5.0 and y is 5.0 to 20.0) is simply referred to as "Fe ２ Mo ｘ O ｙ "Fe composite oxide" and "Fe ２ Mo ｘ O ｙ "Fe composite oxide" or "Fe ２ Mo ｘ O ｙ Here, the term "composite oxide" refers to an oxide containing two or more metals and having a specific peak in X-ray diffraction analysis. ２ Mo ３ O １２ , α-CoMoO ４ , β-CoMoO ４ , and α-Bi ２ Mo ３ O １２ , etc. are composite oxides containing Fe and Mo, Co and Mo, Co and Mo, and Bi and Mo, respectively, and have specific peaks in X-ray diffraction analysis.

[0011] In this specification, "X-ray diffraction analysis using ZnO as an internal standard" is also simply referred to as "X-ray diffraction analysis" or "XRD analysis." "In X-ray diffraction analysis using ZnO as an internal standard, the ratio of the intensity of the maximum peak among the peaks attributed to ZnO at 2θ = 34.2 to 34.6° to the intensity of Fe at 2θ = 19.5 to 22.5°" ２ Mo ｘ O ｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxides is simply referred to as "Fe ２ Mo ｘ O ｙ In X-ray diffraction analysis using ZnO as an internal standard, the peak intensity ratio of β-CoMoO ４ Fe at 2θ = 19.5 to 22.5° relative to the intensity of the maximum peak among the peaks assigned to ２ Mo ｘ O ｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxides is simply referred to as "Fe ２ Mo ｘ O ｙ / β-CoMoO ４ "In X-ray diffraction analysis using ZnO as an internal standard, the peak intensity ratio of α-Bi at 2θ = 27.7 to 28.1° is ２ Mo ３ O １２ Fe at 2θ = 19.5 to 22.5° relative to the intensity of the maximum peak among the peaks assigned to ２ Mo ｘ O ｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxides is simply referred to as "Fe ２ Mo ｘ O ｙ / α-Bi ２ Mo ３ O １２ "In X-ray diffraction analysis using ZnO as an internal standard, the peak intensity ratio of α-CoMoO ４ Fe at 2θ = 19.5 to 22.5° relative to the intensity of the maximum peak among the peaks assigned to ２ Mo ｘ Oｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxides is simply referred to as "Fe ２ Mo ｘ O ｙ / α-CoMoO ４ It is also called the "peak intensity ratio."

[0012] In this specification, the term "X to Y" indicating a range includes X and Y and means "at least X and at most Y." In this specification, "A and / or B" means at least one of A and B, and includes both A and B, or either A or B.

[0013] Preferred embodiments of the present invention will be described below. Note that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the claims. Furthermore, the embodiments described in this specification can be arbitrarily combined to form other embodiments.

[0014] [Catalyst for producing acrolein and / or acrylic acid] The catalyst for producing acrolein and / or acrylic acid according to the present invention comprises Fe ２ Mo ｘ O ｙ In the present invention, Fe ２ Mo ｘ O ｙ The mechanism by which the inclusion of a composite oxide improves the yield of acrolein and / or acrylic acid is presumed to be as follows: In the process of producing acrolein by catalytic gas-phase oxidation of propylene in the presence of a catalyst, a cycle is usually repeated in which propylene is oxidized using oxygen taken up in the catalyst, and then oxygen from the atmosphere is taken up into the catalyst structure to replenish the oxygen consumed by the oxidation. ２ Mo ｘ O ｙ It is presumed that the composite oxide promotes the incorporation of oxygen into the catalyst structure in the above cycle, and that the promotion of oxygen incorporation into the catalyst structure increases the amount of oxygen available for the oxidation of propylene, thereby improving the yield of acrolein and / or acrylic acid.

[0015] Fe according to the present invention ２ Moｘ O ｙ In the composite oxide, x is 1.0 to 5.0. x is preferably 2.0 to 4.0, and particularly preferably 3.0. y is 5.0 to 20.0. y is preferably 8.0 to 14.0, more preferably 10.0 to 13.0, and particularly preferably 12.0. Such values ​​of x and y are preferable because they result in a state in which a large amount of oxygen is incorporated into the catalyst. As a result, the conversion rate of propylene, the yield of acrolein, and the yield of acrylic acid during the catalytic gas-phase oxidation of propylene can be improved.

[0016] That is, Fe according to the present invention ２ Mo ｘ O ｙ The composite oxide is considered to have a particularly high contribution to promoting the incorporation of oxygen into the catalyst structure. ２ Mo ３ O ８ (ICDD reference code: 00-035-1479), Fe ２ Mo ３ O １２ (ICDD reference code: 00-031-0642), Fe ２ Mo ４．２３ O ７．４１ (Fe １．８９ Mo ４．１１ O ７ ) (ICDD reference code: 00-042-0317), Fe ２ Mo ４ O ７ (Fe ８ Mo １６ O ２８ ), Fe ２ Mo ４ O ２０ Preferably, Fe ２ Mo ３ O １２ , Fe ２ Mo ３ O ８ is more preferred, and Fe ２ Mo ３ O １２ These Fe ２ Mo ｘ Oｙ The composite oxide may be contained alone or in a mixture of multiple Fe ２ Mo ｘ O ｙ It may contain a composite oxide, but Fe ２ Mo ３ O １２ is other Fe ２ Mo ｘ O ｙ It is preferable that the content of the oxide is larger than that of the composite oxide.

[0017] The catalyst according to the present invention contains Fe ２ Mo ｘ O ｙ The presence of a composite oxide can be confirmed by measuring X-ray diffraction (XRD). Specifically, it is confirmed that a diffraction peak exists at 2θ=19.5 to 22.5° in the XRD analysis.

[0018] Fe ２ Mo ｘ O ｙ The amount of the composite oxide can be determined by the maximum peak intensity at 2θ=19.5 to 22.5°. ２ Mo ３ O １２ In XRD analysis, Fe has diffraction peaks at 2θ=20.2 to 20.6° and 21.3 to 21.8°. ２ Mo ４．２３ O ７．４１ (Fe １．８９ Mo ４．１１ O ７ In XRD analysis, Fe has diffraction peaks at 2θ=20.6 to 21.0°, 21.4 to 21.7°, and 21.8 to 22.1°. ２ Mo ３ O ８ In XRD analysis, Fe has a diffraction peak at 2θ=19.6 to 20.0°. In the present disclosure, the intensity of the maximum peak among the peaks at 2θ=34.2 to 34.6° attributed to ZnO in an XRD pattern using ZnO as an internal standard is calculated based on the ratio of the intensity of the maximum peak of Fe at 2θ=19.5 to 22.5°. ２ Mo ｘ O ｙThe ratio of the maximum peak intensity among the peaks attributed to the composite oxide (Fe ２ Mo ｘ O ｙ / ZnO peak intensity ratio) ２ Mo ｘ O ｙ It is used as an index of the amount of complex oxides.

[0019] The catalyst according to the present invention comprises Fe ２ Mo ｘ O ｙ Composite oxide (x=1.0 to 5.0, y=5.0 to 20.0) is contained, Fe ２ Mo ｘ O ｙ The Fe / ZnO peak intensity ratio is more than 0.23. ２ Mo ｘ O ｙ If the / ZnO peak intensity ratio exceeds 0.23, Fe ２ Mo ｘ O ｙ Composite oxides (especially Fe ２ Mo ３ O １２ On the other hand, the Fe ２ Mo ｘ O ｙ When the / ZnO peak intensity ratio is 0.23 or less, the Fe present in the catalyst ２ Mo ｘ O ｙ The low amount of composite oxide results in insufficient oxygen uptake into the catalyst during the propylene oxidation reaction, resulting in low propylene conversion and low yields of acrolein and / or acrylic acid.

[0020] Fe ２ Mo ｘ O ｙ The Fe / ZnO peak intensity ratio is preferably 0.24 or more, more preferably 0.31 or more, even more preferably 0.40 or more, and particularly preferably 0.45 or more. Such a ratio is preferable because it allows a large amount of oxygen to be taken up by the catalyst during the propylene oxidation reaction. As a result, the propylene conversion rate, the acrolein yield, and / or the acrylic acid yield during the catalytic gas phase oxidation of propylene can be improved. ２ Moｘ O ｙ The higher the / ZnO peak intensity ratio, the more preferable it is, and therefore the upper limit is not particularly limited, but is, for example, 1.0 or less, 0.80 or less, 0.60 or less, or 0.50 or less.

[0021] As used herein, the term "maximum peak" refers to the peak with the highest intensity in a specific, defined 2θ range in an XRD pattern using ZnO as an internal standard. Furthermore, as used herein, the term "maximum peak intensity" refers to the intensity of the peak with the highest intensity in a specific, defined 2θ range in an XRD pattern using ZnO as an internal standard. The "maximum peak intensity" is positively correlated with the amount of crystalline structure present in the catalyst that exhibits the intensity of the maximum peak. The maximum peak intensity of each crystalline structure (crystalline phase) is a value measured according to the method described in the "X-ray diffraction" section of the Examples below.

[0022] As mentioned above, Fe ２ Mo ｘ O ｙ The composite oxide is Fe ２ Mo ３ O １２ It is preferable that the catalyst according to the present invention is Fe ２ Mo ３ O １２ It can be confirmed by XRD analysis that the Fe content is 0.01%. Specifically, in the XRD analysis, it is confirmed that a diffraction peak exists at 2θ=21.3 to 21.8°. ２ Mo ３ O １２ However, the diffraction peak detected at 2θ=21.3 to 21.8° is not due to Fe. ２ Mo ３ O １２ It is characteristic of Fe ２ Mo ３ O １２ That is, the catalyst according to a preferred embodiment of the present invention is a catalyst for producing acrolein and / or acrylic acid by catalytic gas phase oxidation of propylene in the presence of molecular oxygen or a molecular oxygen-containing gas, and the catalyst is ２Mo ３ O １２ In an X-ray diffraction analysis using ZnO as an internal standard, the intensity of the maximum peak among the peaks attributed to ZnO at 2θ = 34.2 to 34.6° is compared with the intensity of Fe at 2θ = 21.3 to 21.8°. ２ Mo ３ O １２ The ratio of the maximum peak intensity among the peaks attributed to Fe ２ Mo ３ O １２ / ZnO peak intensity ratio) exceeds 0.23. ２ Mo ３ O １２ The Fe / ZnO peak intensity ratio is preferably 0.24 or more, more preferably 0.31 or more, even more preferably 0.40 or more, and particularly preferably 0.45 or more. ２ Mo ３ O １２ The / ZnO peak intensity ratio is 1.0 or less, 0.80 or less, 0.60 or less, or 0.50 or less.

[0023] As mentioned above, the catalyst contains Fe. ２ Mo ３ O １２ Various crystal structures (crystal phases) other than Fe may be included. ２ Mo ３ O １２ Fe crystals ２ Mo ３ O １２ When containing crystals with a structure other than Fe at 2θ = 19.5 to 22.5° ２ Mo ３ O １２ The peak intensity of crystals with structures other than those of Fe at 2θ = 21.3 to 21.8° ２ Mo ３ O １２ The peak with the highest intensity was determined as Fe. ２ Mo ｘ O ｙ As the peak of the composite oxide, the ratio to the maximum peak intensity among the peaks attributable to ZnO in the 2θ range of 34.2 to 34.6° is calculated.

[0024] Alternatively or additionally, in the catalyst of the present invention, Mo is preferably present in a specific ratio relative to Fe. Specifically, the molar ratio of Mo to Fe (Mo / Fe) in the catalyst is, for example, more than 4.1 and less than 23.0, preferably 4.2 to 16.4, more preferably 4.3 to 12.2, and particularly preferably 5.5 to 9.0. In such a range, Fe ２ Mo ｘ O ｙ This is preferable because it is easy to form a composite oxide.

[0025] Fe ２ Mo ｘ O ｙ The composite oxide is Fe ２ Mo ｘ O ｙ A specific ratio of the ZnO peak intensity is preferable because it allows a large amount of oxygen to be taken up by the catalyst during the propylene oxidation reaction. However, the larger the amount of Fe or Mo, the greater the amount of Fe ２ Mo ｘ O ｙ There is a possibility that a large amount of composite oxides are formed. In the (Fe / Mo) shown in the following formula 1, Fe ２ Mo ｘ O ｙ / ZnO peak intensity ratio (molar ratio gradient distribution Fe ２ Mo ｘ O ｙ / ZnO peak intensity ratio) is preferably 2.15 to 10.0. ２ Mo ｘ O ｙ / ZnO peak intensity ratio, regardless of the amount of Fe or Mo, ２ Mo ｘ O ｙ This indicates that a large amount of composite oxide is present. As a result, the oxidation of propylene can be promoted using the oxygen captured in the catalyst, which is preferable.

[0026]

[0027] In the above formula 1, Fe ２ Mo ｘ O ｙ / ZnO is the ratio of the intensity of the maximum peak among the peaks attributed to ZnO at 2θ=34.2 to 34.6° to the intensity of Fe at 2θ=19.5 to 22.5° in XRD analysis using ZnO as an internal standard. ２ Mo ｘ O ｙ The molar ratio of Fe to Mo is the ratio of the maximum peak intensity among the peaks attributed to the composite oxide; Fe / Mo is the molar ratio of Fe to Mo. In this specification, the molar ratio gradient distribution Fe defined by the above formula 1 ２ Mo ｘ O ｙ / ZnO peak intensity ratio is simply referred to as "molar ratio gradient distribution Fe ２ Mo ｘ O ｙ / ZnO peak intensity ratio.

[0028] Here, the molar ratio gradient distribution Fe ２ Mo ｘ O ｙ The / ZnO peak intensity ratio is more preferably 2.2 to 8.0, even more preferably 2.6 to 4.0, and particularly preferably more than 2.6 but not more than 3.2. Within this range, regardless of the amount of Fe or Mo, ２ Mo ｘ O ｙ This indicates that a large amount of composite oxide is present. As a result, the oxidation of propylene can be promoted using the oxygen captured in the catalyst, which is preferable.

[0029] The catalyst according to the present invention has a diffraction peak detected at 2θ=19.5 to 22.5°. ２ Mo ｘ O ｙ The composite oxide is essentially contained. ２ Mo ｘ O ｙ In the composite oxide, Fe ３＋ It is preferable that the alloy has Fe. ２＋ Fe having ２ Mo ｘ O ｙ In the case of Fe, the oxygen supply capacity is reduced, and the reduction of Mo on the surface proceeds. As a result, acrolein and acrylic acid are easily oxidized, resulting in a decrease in yield. Therefore, the catalyst according to the present invention is２＋ It is preferable that the composition is substantially free of

[0030] Specifically, the total Fe ions (Fe ３＋ +Fe ２＋ ) to Fe ３＋ The molar ratio of [Fe ３＋ / (Fe ３＋ +Fe ２＋ ) is preferably greater than 0.5, more preferably 0.8 or more, and even more preferably 0.9 or more (upper limit: 1). ３＋ / (Fe ３＋ +Fe ２＋ ) is preferably in the above range, since the oxidation of propylene can be promoted using the oxygen captured in the catalyst. ３＋ +Fe ２＋ ) to Fe ３＋ The molar ratio (Fe ３＋ / (Fe ３＋ +Fe ２＋ )) is measured by X-ray absorption fine structure (XAFS).

[0031] The catalyst according to the present invention preferably further contains cobalt (Co). Co is preferably present in the form of a composite oxide with Mo (CoMoO ４ ) (for example, α-cobalt molybdate (α-CoMoO ４ ), β-type cobalt molybdate (β-CoMoO ４ )) is preferably formed. These function to incorporate oxygen from the gas phase into the catalyst structure and supply it to active species. Therefore, the presence of Co in the catalyst can further promote the incorporation of oxygen into the catalyst structure, thereby further improving the propylene conversion rate and the yield of acrolein and / or acrylic acid.

[0032] The catalyst according to the present invention is β-CoMoO ４ It can be confirmed by XRD analysis. Specifically, it can be confirmed by the presence of a diffraction peak at 2θ=26.3 to 26.7° in the XRD analysis. ４However, the diffraction peak detected at 2θ = 26.3 to 26.7° is not the same as that of β-CoMoO. ４ and is characterized by β-CoMoO ４ This can be used as an indicator of the presence of

[0033] The catalyst according to the present invention is β-CoMoO ４ In the case where the compound contains β-CoMoO in XRD analysis using ZnO as an internal standard, ４ Fe at 2θ = 19.5 to 22.5° relative to the intensity of the maximum peak among the peaks assigned to ２ Mo ｘ O ｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxide (Fe ２ Mo ｘ O ｙ / β-CoMoO ４ The peak intensity ratio is preferably more than 0.07, more preferably 0.075 to 0.50, even more preferably 0.10 to 0.30, and particularly preferably 0.150 or more and less than 0.190. ２ Mo ｘ O ｙ / β-CoMoO ４ With this peak intensity ratio, oxygen is efficiently taken up into the catalyst, and as a result, at least one (preferably all) of the propylene conversion rate, the acrolein yield, and the acrylic acid yield during the catalytic vapor-phase oxidation of propylene can be further improved.

[0034] The catalyst according to the present invention is α-CoMoO ４ It can be confirmed by XRD analysis. Specifically, it can be confirmed by the presence of a diffraction peak at 2θ=13.9 to 14.3° in the XRD analysis. ４ The crystal structure of is also observed in the XRD pattern at 2θ = 13.9 to 14.3°. However, the diffraction peak detected at 2θ = 13.9 to 14.3° is α-CoMoO ４ and is characterized by α-CoMoO ４This can be used as an indicator of the presence of the crystal structure.

[0035] The catalyst according to the present invention is α-CoMoO ４ In the case where the compound contains α-CoMoO in XRD analysis using ZnO as an internal standard, ４ Fe at 2θ = 19.5 to 22.5° relative to the intensity of the maximum peak among the peaks assigned to ２ Mo ｘ O ｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxide (Fe ２ Mo ｘ O ｙ / α-CoMoO ４ The peak intensity ratio is, for example, 0.49 or more, preferably 0.54 to 10.00, more preferably 0.70 to 5.00, even more preferably 0.82 to 2.00, and most preferably 0.90 or more and less than 1.05. ２ Mo ｘ O ｙ / α-CoMoO ４ With this peak intensity ratio, oxygen is efficiently taken up into the catalyst, and as a result, at least one (preferably all) of the propylene conversion rate, the acrolein yield, and the acrylic acid yield during the catalytic vapor-phase oxidation of propylene can be further improved.

[0036] Alternatively or additionally, in the catalyst of the present invention, Mo is preferably present in a specific ratio relative to Co. Specifically, the catalyst preferably contains Mo and Co in a composition where the molar ratio of Mo to Co (Mo / Co) is 1.05 or more, more preferably where the molar ratio of Mo to Co (Mo / Co) is 1.05 or more and 4.00 or less, even more preferably where the molar ratio of Mo to Co (Mo / Co) is 1.50 or more and 3.00 or less, and particularly preferably where the molar ratio of Mo to Co (Mo / Co) is 2.00 or more and 2.80 or less. With such a composition, α-CoMoO ４ and β-CoMoO ４ While forming Fe２ Mo ｘ O ｙ This is preferable because it does not inhibit the formation of the composite oxide, and as a result, at least one (preferably all) of the propylene conversion rate, the acrolein yield, and the acrylic acid yield during catalytic vapor-phase oxidation of propylene can be further improved.

[0037] Alternatively or additionally, the catalyst of the present invention preferably contains Co in a specific ratio relative to Fe. Specifically, the molar ratio of Co to Fe (Co / Fe) in the catalyst is preferably 1.1 to 10.3, more preferably 1.8 to 7.8, and particularly preferably 2.2 to 4.5.

[0038] Alternatively or in addition to the above, the catalyst according to the present invention preferably further contains bismuth (Bi). Bi is an α-Bi complex oxide with Mo. ２ Mo ３ O １２ This α-Bi ２ Mo ３ O １２ can function to promote the oxidation of propylene and further improve the conversion of propylene and the yield of acrolein and / or acrylic acid.

[0039] The catalyst according to the present invention is α-Bi ２ Mo ３ O １２ It can be confirmed by XRD analysis. Specifically, it can be confirmed by the presence of a diffraction peak at 2θ=27.7 to 28.1° in the XRD analysis. ２ Mo ３ O １２ The crystal structure of α-Bi is also observed in the XRD pattern at positions other than 2θ=27.7 to 28.1°. However, the diffraction peak detected at the position of 2θ=27.7 to 28.1° is not α-Bi. ２ Mo ３ O １２ It is characteristic of α-Bi ２ Mo ３ O １２ This can be used as an indicator of the presence of the crystal structure.

[0040] The catalyst according to the present invention is α-Bi ２ Mo ３ O １２ In the case where the compound contains α-Bi, in XRD analysis using ZnO as an internal standard substance, ２ Mo ３ O １２ Fe at 2θ = 19.5 to 22.5° relative to the intensity of the maximum peak among the peaks assigned to ２ Mo ｘ O ｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxide (Fe ２ Mo ｘ O ｙ / α-Bi ２ Mo ３ O １２ The peak intensity ratio is preferably 0.08 or more, more preferably 0.08 to 0.50, even more preferably 0.15 to 0.35, and particularly preferably 0.16 to 0.20. ２ Mo ｘ O ｙ / α-Bi ２ Mo ３ O １２ The peak intensity ratio can promote the oxidation of propylene and function to further improve the conversion rate of propylene and the yield of acrolein and / or acrylic acid.

[0041] Alternatively or additionally, in the catalyst of the present invention, Mo is preferably present in a specific composition relative to Bi. Specifically, the catalyst preferably contains Mo and Bi in a composition in which the molar ratio of Mo to Bi (Mo / Bi) is 3.3 or more, more preferably in a composition in which the molar ratio of Mo to Bi (Mo / Bi) is 5.5 or more and 8.3 or less, and particularly preferably in a composition in which the molar ratio of Mo to Bi (Mo / Bi) is 6.30 or more and 7.70 or less. With such a composition, α-Bi ２ Mo ３ O １２ The crystals of β-CoMoO ４As a result, at least one (preferably all) of the propylene conversion rate, the acrolein yield, and the acrylic acid yield during the catalytic vapor phase oxidation of propylene can be further improved.

[0042] Alternatively or additionally, in the catalyst of the present invention, Bi is preferably present in a specific ratio relative to Fe. Specifically, the molar ratio of Bi to Fe in the catalyst (Bi / Fe) is preferably 0.2 to 2.9, more preferably 0.6 to 1.6, and particularly preferably 0.8 to 1.3. With such a composition, α-Bi ２ Mo ３ O １２ While forming Fe ２ Mo ｘ O ｙ This is preferable because it does not inhibit the formation of the composite oxide, and as a result, at least one (preferably all) of the propylene conversion rate, the acrolein yield, and the acrylic acid yield during catalytic vapor-phase oxidation of propylene can be further improved.

[0043] That is, in one embodiment of the present invention, the catalyst according to the present invention contains 4.2 to 16.4 mol of Mo, 0.2 to 2.9 mol of Bi, and 1.1 to 10.3 mol of Co per mol of Fe. In one embodiment of the present invention, the catalyst according to the present invention contains 4.3 to 12.2 mol of Mo, 0.6 to 1.6 mol of Bi, and 1.8 to 7.8 mol of Co per mol of Fe. In one embodiment of the present invention, the catalyst according to the present invention contains 5.5 to 9.0 mol of Mo, 0.8 to 1.3 mol of Bi, and 2.2 to 4.5 mol of Co per mol of Fe.

[0044] Alternatively or additionally, when the catalyst of the present invention further contains Co and Bi, β-CoMoO ４ and α-Bi ２ Mo ３ O １２ Specifically, the catalyst of the present invention preferably contains β-CoMoO ４ and α-Bi ２ Mo ３ O １２ It is preferable that β-CoMoO４ and α-Bi ２ Mo ３ O １２ The presence of the specified ratio can be confirmed by XRD analysis using ZnO as an internal standard substance.

[0045] In XRD analysis using ZnO as an internal standard, α-Bi at 2θ = 27.7 to 28.1° ２ Mo ３ O １２ The intensity of the maximum peak among the peaks assigned to β-CoMoO at 2θ = 26.3 to 26.7° ４ The ratio of the maximum peak intensity among the peaks attributed to (β-CoMoO ４ / α-Bi ２ Mo ３ O １２ The peak intensity ratio is, for example, 2.33 or less, preferably less than 1.95, more preferably 1.90 or less, even more preferably 1.50 or less, and particularly preferably 1.10 or less. ４ / α-Bi ２ Mo ３ O １２ When the peak intensity ratio exceeds 2.33, it is β-CoMoO ４ There are too many crystals of α-Bi ２ Mo ３ O １２ Oxygen consumption and β-CoMoO ４ In the present embodiment, the balance of oxygen compensation by ZnO is lost and the yield is reduced, which is not preferable. ２ Mo ３ O １２ The intensity of the maximum peak among the peaks assigned to β-CoMoO at 2θ = 26.3 to 26.7° ４ The ratio of the maximum peak intensity among the peaks attributed to (β-CoMoO ４ / α-Bi ２ Mo ３ O １２In one embodiment of the present invention, the catalyst is β-CoMoO ４ and α-Bi ２ Mo ３ O １２ In the X-ray diffraction analysis, α-Bi at 2θ=27.7 to 28.1° is ２ Mo ３ O １２ The ratio of the intensity of the maximum peak among the peaks assigned to 2θ=26.3 to 26.7° to the intensity of the maximum peak among the peaks assigned to 2θ=26.3 to 26.7° is 0.70 to 2.33.

[0046] The catalyst according to the present invention may further contain nickel (Ni), and preferably contains Ni. When the catalyst contains Ni, the catalyst contains Ni in a composition in which the molar ratio of Ni to Fe (Ni / Fe) is preferably 0.2 to 5.0, more preferably 0.4 to 2.6, and particularly preferably 0.7 to 1.0. With such a composition, Fe ２ Mo ｘ O ｙ Since the formation of propylene is not inhibited, at least one (preferably all) of the propylene conversion rate, the acrolein yield, and the acrylic acid yield during the catalytic vapor phase oxidation of propylene can be further improved.

[0047] The catalyst of the present invention is a catalyst of formula 2: Fe １ Mo ａ Bi ｂ Co ｃ Ni ｄ X ｅ O ｆ The catalyst having the composition of the above formula 2 is composed of a composite oxide containing two or more elements selected from the group consisting of Bi, Co, Ni, Fe, Mo and X, and may have the composition of the above formula 2 as a whole. ２ Mo ｘ O ｙ Composite oxides (especially Fe ２ Mo ３ O １２composite oxide), α-CoMoO ４ , β-CoMoO ４ , and α-Bi ２ Mo ３ O １２ It is preferable that the composite oxide contains a predetermined amount of the above-mentioned composite oxides, but other composite oxides may also be contained.

[0048] In the above formula 2, X is at least one element selected from the group consisting of vanadium (V), tungsten (W), antimony (Sb), cerium (Ce), titanium (Ti), manganese (Mn), potassium (K), germanium (Ge), chromium (Cr), sodium (Na), rubidium (Rb), cesium (Cs), and lithium (Li). X is preferably at least one element selected from the group consisting of antimony (Sb), cerium (Ce), manganese (Mn), potassium (K), germanium (Ge), chromium (Cr), sodium (Na), rubidium (Rb), cesium (Cs), and lithium (Li), more preferably at least one element selected from the group consisting of potassium (K), sodium (Na), rubidium (Rb), cesium (Cs), and lithium (Li), and particularly preferably potassium (K).

[0049] In the above formula 2, a is the atomic ratio of molybdenum (Mo) to one atom of iron (Fe), for example, greater than 4.1 and less than 23.0, preferably 4.2 to 16.4, more preferably 4.3 to 12.2, and particularly preferably 5.5 to 9.0. b is the atomic ratio of bismuth (Bi) to one atom of Fe, preferably 0.2 to 2.9, more preferably 0.6 to 1.6, and particularly preferably 0.8 to 1.3. c is the atomic ratio of cobalt (Co) to one atom of Fe, preferably 1.1 to 10.3, more preferably 1.8 to 7.8, and particularly preferably 2.2 to 4.5. d is the atomic ratio of nickel (Ni) to one atom of Fe, preferably 0.2 to 5.0, more preferably 0.4 to 2.6, and particularly preferably 0.7 to 1.0. e is the atomic ratio of X to Fe atom, and is preferably 0.01 to 0.30, more preferably 0.03 to 0.10, and particularly preferably 0.04 to 0.05. f is a value determined by the oxidation state of each element.

[0050] The catalyst according to the present invention comprises Fe ２ Mo ｘ O ｙ The catalyst may be a supported catalyst in which the catalyst component containing the composite oxide is supported on a carrier, or may be a catalyst containing Fe ２ Mo ｘ O ｙ The catalyst may be a non-supported catalyst in which the catalyst component containing the composite oxide is not supported on a carrier. ２ Mo ｘ O ｙThis is a supported catalyst in which a catalyst component containing a composite oxide is supported on a carrier. The carrier that can be used in this case is not particularly limited, and known carriers can be used, but it is preferable that the carrier be inactive against acrolein and acrylic acid. Specific examples include inorganic oxides such as silica, alumina, titania, zirconia, magnesia, steatite, and cordierite; composite oxides thereof such as alumina-silica, silica-magnesia, and silica-magnesia-alumina; crystalline metallosilicates such as zeolite; metals and alloys such as stainless steel and aluminum; and inorganic compounds such as activated carbon, silicon carbide, and silicon nitride. Of these, it is preferable to use silica, alumina, titania, zirconia, or composite oxides thereof as the carrier.

[0051] When the catalyst according to the present invention is a supported catalyst, the shape of the support is not particularly limited, and examples thereof include spherical, cylindrical, and columnar shapes. The size of the support is also not particularly limited, and a size that can be used when packed in a reaction tube may be selected. Specifically, the maximum outer diameter of the catalyst is preferably 3 to 20 mm, and more preferably 4 to 8 mm.

[0052] The loading rate of the catalyst component can be appropriately selected depending on the ease of operation control in the reactor, catalyst life, etc. Specifically, the loading rate of the catalyst component is preferably 50 to 200 mass%, more preferably 90 to 150 mass%, relative to 100 mass% of the carrier. In this specification, the loading rate of the catalyst component in a supported catalyst is measured by the following method.

[0053] [Measurement of Support Ratio of Supported Catalyst] The support ratio of the catalyst components in a supported catalyst is the percentage of the total mass of the catalyst components relative to the total mass of the support, and can be calculated using the following formula 3. Here, the total mass of the catalyst components is the value obtained by subtracting the total mass of the support (B) from the total mass of the catalyst (A). Note that the separation of the catalyst components from the supported catalyst can be carried out by the following procedure.

[0054]

[0055] [Separation of catalytic components from supported catalyst for measuring loading rate] (1) 100 g of supported catalyst is collected and calcined at 470°C for 6 hours in an air atmosphere. (2) Next, the mass of the calcined catalyst (A [g]) is measured. (3) The calcined catalyst is placed in 400 mL of a 10% aqueous sodium hydroxide solution and boiled for 30 minutes to dissolve the catalytic components. (4) The solution containing the dissolved catalytic components and support components is passed through a mesh corresponding to the shape of the support, and the support components are separated from the solution containing the dissolved catalytic components. (5) The support components remaining on the mesh after separation are washed by boiling for 30 minutes in 400 mL of distilled water. (6) The washed support components are washed three more times with 100 mL of distilled water. (7) The support components washed with distilled water are dried at 200°C for 1 hour, and then the mass of the dried support (B [g]) is measured.

[0056] [X-ray diffraction analysis using ZnO as an internal standard] Whether or not a catalyst is the present invention is confirmed by confirming whether or not the diffraction pattern obtained by XRD analysis using ZnO as an internal standard has a predetermined profile. The X-ray diffraction analysis using ZnO as an internal standard is performed using a sample glass cell prepared by the following procedure.

[0057] <1> Separation of catalytic components from supported catalysts for X-ray diffraction analysis: In the case of supported catalysts, it is necessary to separate the catalytic components from the support components in order to prepare samples containing internal standards. To separate the catalytic components of supported catalysts, 50 g of the catalyst (supported catalyst before separation of the catalytic components and the support components) is placed in a cylindrical rotating machine with a radius of 14 cm and equipped with a single baffle plate inside, rotated at 50 rpm for 30 minutes, and then the peeled powder is recovered. The recovered powder is sieved to a particle size of 150 μm or less to obtain a powder of the catalytic components.

[0058] In addition, in the case of a non-supported catalyst (molded catalyst) that is not supported on a carrier, the same procedure can be carried out and sieved to obtain a powder of the catalyst component for X-ray diffraction analysis.

[0059] <2> Preparation of a sample containing a powdered internal standard: 1 g of the catalyst component powder obtained in <1> and ZnO as an internal standard were weighed out so that the mass ratio of ZnO to catalyst was 1:10. The weighed catalyst and ZnO were placed in an agate mortar, and 10 ml of acetone was added dropwise and mixed for 5 minutes. Mixing for more than 5 minutes is not recommended, as this may cause mechanochemical changes in the crystals, such as phase transition. The dried mixture was dried at 50°C for 1 hour to prepare a sample containing a powdered internal standard.

[0060] <3> Preparation of a sample glass cell containing an internal standard substance. Preparation of a sample containing an internal standard substance can be performed according to the operating procedures provided with the X-ray diffraction analyzer. For example, a glass sample cell is filled with the powdered sample containing the internal standard substance prepared in <2> in the amount specified in the operating procedures provided with the X-ray diffraction analyzer. A plate-shaped sample glass cell containing the internal standard substance is prepared by pressing the measurement surface flat with a glass plate or the like.

[0061] <4> X-ray Diffraction Analysis X-ray diffraction analysis can be performed using a commercially available X-ray diffraction analyzer. Specifically, a sample glass cell containing ZnO prepared in <3> as an internal standard is installed in the X-ray diffraction analyzer according to the operating procedures provided with the X-ray diffraction analyzer. Next, measurements are performed under the measurement conditions described below. Based on the X-ray diffraction pattern (XRD pattern) obtained as a result of the measurement, peaks are identified and intensities are calculated using analysis software provided with the X-ray diffraction analyzer. Each peak is identified by analysis based on the description of the reference code in the ICDD, analysis by the Rietveld method, or analysis software using the Rietveld method.

[0062] [Catalyst manufacturing method] (Fe ２ Mo ｘ O ｙPreparation of Precursor) An iron-containing raw material (Fe-containing raw material) stored at a predetermined temperature is added to a solvent to prepare a solution (Fe-containing solution). Next, a molybdenum-containing raw material (Mo-containing raw material) stored at a predetermined temperature is added to a solvent to prepare a solution (Mo-containing solution). The Mo-containing solution is added to the Fe-containing solution, and the mixture is stirred at a predetermined temperature to obtain an Fe-Mo-containing suspension. A predetermined amount of a compound having an NH structure is added to this Fe-Mo-containing suspension, and the mixture is further stirred. After stirring, the mixture is evaporated to dryness to obtain Fe. ２ Mo ｘ O ｙ After evaporation to dryness, the dried product may be dried and / or pulverized, if necessary.

[0063] The Mo-containing raw material is not particularly limited as long as it ultimately produces molybdenum oxide (by firing). Specifically, molybdenum oxides (e.g., molybdenum trioxide, molybdic acid); hydroxides; halides such as chlorides, bromides, and iodides; inorganic salts such as nitrates, carbonates, and sulfates; organic acid salts such as formates, acetates, oxalates, and citrates; and oxoacids or oxoacid salts (e.g., ammonium salts or alkali metal salts of oxoacids). The Mo-containing raw material may be in the form of a hydrate. The Mo-containing raw material may be used alone or in combination of two or more. Among these, from the viewpoint of solubility in solvents, oxoacids or oxoacid salts or hydrates thereof are preferred, and paramolybdic acid or ammonium paramolybdate or hydrates thereof (e.g., ammonium paramolybdate(VI) tetrahydrate) are more preferred.

[0064] The Fe-containing raw material is not particularly limited as long as it ultimately produces iron oxide (by calcination). Specifically, iron oxides; hydroxides; halides such as chlorides, bromides, and iodides; inorganic salts such as nitrates, carbonates, and sulfates; organic acid salts such as formates, acetates, oxalates, and citrates; and oxoacids or oxoacid salts (e.g., ammonium salts or alkali metal salts of oxoacids). The Fe-containing raw material may be in the form of a hydrate. The Fe-containing raw material may be used alone or in combination of two or more. Of these, nitrates and hydrates thereof (e.g., iron (III) nitrate nonahydrate) are preferred from the viewpoint of solubility in solvents.

[0065] The Mo-containing raw material, the Fe-containing raw material, and the compound having an NH structure are preferably stored at 0°C to 40°C, more preferably at 10°C to 38°C, and even more preferably at 20°C to 35°C. In cold regions, the raw materials may be stored at temperatures below 0°C, which is undesirable because adding these to a solvent causes localized freezing of the solvent and inhibits the reaction of the Mo-containing raw material and the Fe-containing raw material. Furthermore, if a Mo-containing raw material or an Fe-containing raw material stored at a temperature higher than 40°C is used, the compound having an NH structure may evaporate or denature when added, resulting in the formation of Fe. ２ Mo ｘ O ｙ This is undesirable because it inhibits the formation of complex oxides.

[0066] The mixing ratio of the Mo-containing raw material and the Fe-containing raw material is preferably a ratio that results in the composition described above. In the present disclosure, the composition of the catalyst is controlled by the mixing ratio (addition amount, charged amount) of each metal raw material.

[0067] As the solvent, water (deionized water, tap water, distilled water, ion-exchanged water) can be used. The above solvents may be used alone or in combination of two or more. Among these, ion-exchanged water is preferred. The solvents used to prepare the Fe-containing solution and the Mo-containing solution may be the same or different, but are preferably the same.

[0068] The compound having an -NH structure may be any compound having an -NH bond in the molecule. Even if a compound not having an -NH bond is added, the specific Fe as defined in the present invention can be obtained. ２ Mo ｘ O ｙ / ZnO peak intensity ratio (see Comparative Example 2 below). Examples of compounds having an NH structure include ammonium salts of inorganic acids such as ammonium chloride, ammonium sulfate, ammonium amidosulfate, ammonium nitrate, monoammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium diphosphite, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfide, ammonium borate, and ammonium fluoroborate; ammonium formate, ammonium acetate, ammonium oxalate (diammonium oxalate), ammonium hydrogen oxalate, ammonium benzoate, monoammonium citrate, diammonium citrate, triammonium citrate, ammonium lactate, and ammonium phthalate. ammonium salts of organic acids such as ammonium succinate, monoammonium tartrate, diammonium tartrate, and ammonium aspartate; amine compounds such as ammonia, methylamine, ethylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, propylamine, butylamine, 2-ethylbutylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, allylamine, diallylamine, cyclobutylamine, cyclohexylamine, laurylamine, aniline, diphenylamine, urea, and thiourea; melamine, cyanuric acid (isocyanuric acid), and melamine cyanurate.

[0069] In a preferred embodiment of the present invention, the compound having an NH structure is at least one selected from the group consisting of ammonium acetate, ammonia, ammonium carbonate, melamine, ammonium nitrate, urea, cyanuric acid (isocyanuric acid), ammonium chloride, ammonium bicarbonate, ammonium oxalate, melamine cyanurate, methylamine, dimethylamine, ethylamine, diethylamine, allylamine, diallylamine, and aniline. In a more preferred embodiment of the present invention, the compound having an NH structure is at least one selected from the group consisting of ammonium nitrate, ammonium carbonate, ammonium acetate, ammonia, urea, melamine, cyanuric acid (isocyanuric acid), ammonium oxalate, and melamine cyanurate. In a further preferred embodiment of the present invention, the compound having an NH structure is at least one selected from the group consisting of ammonium nitrate, ammonium carbonate, ammonium acetate, ammonia, urea, melamine, and cyanuric acid (isocyanuric acid). In a particularly preferred embodiment of the present invention, the compound having an NH structure is ammonium acetate, ammonia, or urea. The catalyst according to the present invention can be produced more efficiently using these compounds. The compounds having an NH structure may be used alone or in combination of two or more.

[0070] The amount of the compound having an NH structure to be added is selected so that the number of NH structures is an appropriate ratio relative to the amount of the Fe-containing raw material and the Mo-containing raw material. Here, the "number of NH structures" means the number of -NH- structures (the number of nitrogen atoms constituting the -NH structure) present in the compound having an NH structure. For example, ammonium carbonate has a (NH ４ ) ２ CO ３ It has the structure of ammonium carbonate, and has two NH structures in one molecule. Therefore, the number of NH structures in one mole of ammonium carbonate is two.

[0071] The amount of the compound having an NH structure added is preferably such that the number of NH structures is 0.01 to 1.00 moles per mole of the Mo-containing raw material (molybdenum (in molybdenum equivalent) present in the Mo-containing raw material) and 0.50 to 6.9 moles per mole of the Fe-containing raw material (iron (in iron equivalent) present in the Fe-containing raw material). The amount of the compound having an NH structure added is more preferably such that the number of NH structures is 0.1 to 0.6 moles per mole of the Mo-containing raw material (in molybdenum equivalent) and 1.1 to 4.8 moles per mole of the Fe-containing raw material (in iron equivalent). The amount of the compound having an NH structure added is even more preferably such that the number of NH structures is 0.20 to 0.40 moles per mole of the Mo-containing raw material (in molybdenum equivalent) and 1.7 to 3.4 moles per mole of the Fe-containing raw material (in iron equivalent). The amount of the compound having an NH structure to be added is particularly preferably an amount such that the number of NH structures is 0.25 to 0.35 mol per mol of the Mo-containing raw material (equivalent to molybdenum) and 1.75 to 2.50 mol per mol of the Fe-containing raw material (equivalent to iron).

[0072] That is, in a preferred embodiment of the present invention, the compound having an NH structure is added so that the number of NH structures per mole of the Mo-containing raw material (equivalent to molybdenum) is 0.01 to 1.00 moles and the number of NH structures per mole of the Fe-containing raw material (equivalent to iron) is 0.50 to 6.9 moles. In a more preferred embodiment of the present invention, the compound having an NH structure is added so that the number of NH structures per mole of the Mo-containing raw material (equivalent to molybdenum) is 0.1 to 0.6 moles and the number of NH structures per mole of the Fe-containing raw material (equivalent to iron) is 1.1 to 4.8 moles. In an even more preferred embodiment of the present invention, the compound having an NH structure is added so that the number of NH structures per mole of the Mo-containing raw material (equivalent to molybdenum) is 0.20 to 0.40 moles and the number of NH structures per mole of the Fe-containing raw material (equivalent to iron) is 1.7 to 3.4 moles. In a particularly preferred embodiment of the present invention, the compound having an NH structure is added so that the number of NH structures per mole of the Mo-containing raw material (equivalent to molybdenum) is 0.25 to 0.35 moles and the number of NH structures per mole of the Fe-containing raw material (equivalent to iron) is 1.75 to 2.50 moles. By adding the compound having an NH structure in such a ratio, Fe２ Mo ｘ O ｙ The / ZnO peak intensity ratio can be set within a desired range.

[0073] The stirring of the Fe—Mo-containing suspension may be accompanied by heating. The temperature at which the Fe—Mo-containing suspension is stirred is not particularly limited, and is preferably 20°C or higher, more preferably 25°C or higher, even more preferably 30°C or higher, and is preferably 100°C or lower, more preferably 90°C or lower. When stirring the Fe—Mo-containing suspension continuously, the stirring time is not particularly limited, and may be 1 hour or longer, 3 hours or longer, or 10 hours or longer, or may be 360 ​​hours or shorter, 240 hours or shorter, or 120 hours or shorter. The Fe—Mo-containing suspension may be subjected to a drying step immediately after preparation. Alternatively, the stirring may be continued before the drying step of the Fe—Mo-containing suspension.

[0074] (Drying step of Fe—Mo-containing suspension) If necessary, the Fe—Mo-containing suspension may be concentrated and / or evaporated to dryness to obtain a cake-like solid, which may then be further dried to obtain a solid (dried product). The evaporation to dryness conditions are not particularly limited. For example, evaporation to dryness is preferably carried out at a temperature of 100 to 250° C. The evaporation to dryness time is not particularly limited, but from the viewpoint of catalyst production efficiency, it is preferably 1 hour or more, more preferably 5 hours or more, and preferably 48 hours or less, more preferably 24 hours or less.

[0075] Furthermore, known drying methods such as heating and decompression may be employed. For example, a powdery dried product may be obtained using a spray dryer, drum dryer, or the like. Alternatively, a block-shaped or flake-shaped dried product may be obtained by heating using a box dryer, tunnel dryer, or the like. Examples of the gas to be circulated under airflow or the atmospheric gas in a non-aerated environment include inert gases such as nitrogen and oxygen-containing gases such as air. When drying is performed by heating, it is preferable to perform the drying treatment at a temperature of, for example, 100 to 250°C. The drying time is not particularly limited, but from the viewpoint of catalyst production efficiency, it is preferably 1 hour or more, more preferably 2 hours or more, and preferably 48 hours or less, and more preferably 24 hours or less. When drying is performed under reduced pressure, a vacuum dryer or the like may be used to dry the raw material mixture under reduced pressure to obtain a block-shaped or flake-shaped dried product.

[0076] (Fe when other metal elements other than Fe and Mo are contained ２ Mo ｘ O ｙ Preparation of Precursors) When the catalyst contains oxides containing metal elements other than iron and molybdenum, the metal-containing raw materials may be added to the solvent all at once, or two or more of them may be added separately. For example, when the catalyst contains oxides of Fe, Mo, Co, Ni, Bi, and K, it is preferable to separately prepare a Co—Ni-containing solution (Solution A) containing a Co-containing raw material and a Ni-containing raw material, an Fe—Bi-containing solution (Solution B) containing an Fe-containing raw material and a Bi-containing raw material, a Mo-containing solution (Solution C) containing a Mo-containing raw material, and a K-containing solution (Solution D) containing a K-containing raw material. Here, too, it is preferable to use Fe-containing raw materials and Mo-containing raw materials that have been stored at 0°C to 40°C before use.

[0077] When the catalyst according to the present invention contains other metal elements in addition to the above, a raw material containing the metal element (metal-containing raw material) is appropriately selected. For example, oxides; hydroxides; halides such as chlorides, bromides, and iodides; inorganic salts such as nitrates, carbonates, and sulfates; organic acid salts such as formates, acetates, oxalates, and citrates; and oxoacids or oxoacid salts (e.g., ammonium salts or alkali metal salts of oxoacids) of the metals constituting the catalyst can be used. The metal-containing raw material may be in the form of a hydrate. The metal-containing raw materials may be used alone or in combination of two or more. Among these, nitrates and hydrates thereof (e.g., cobalt(II) nitrate hexahydrate, nickel(II) nitrate hexahydrate, bismuth(III) nitrate pentahydrate, and potassium nitrate) are preferred from the viewpoint of solubility in solvents.

[0078] Solution A can be prepared by adding a Co-containing raw material and a Ni-containing raw material to a solvent. Solution B can be prepared by adding an Fe-containing raw material and a Bi-containing raw material to a solvent. To promote dissolution, solution B is preferably prepared by adding an acid to the solvent in addition to the Fe-containing raw material and the Bi-containing raw material. Examples of the acid that can be used include nitric acid, hydrochloric acid, and sulfuric acid. The acid may be added in its pure form or in the form of a solution (e.g., an aqueous solution). The amount of acid added may be an amount that can sufficiently dissolve the Fe-containing raw material and the Bi-containing raw material, and can be appropriately selected depending on the type of the Fe-containing raw material and the Bi-containing raw material. Solution C can be prepared by adding a Mo-containing raw material to a solvent. Solution D can be prepared by adding a K-containing raw material to a solvent.

[0079] The concentrations of the Co-containing raw material and the Ni-containing raw material in solution A, the Fe-containing raw material and the Bi-containing raw material in solution B, the Mo-containing raw material in solution C, and the K-containing raw material in solution D are not particularly limited and can be appropriately selected depending on the types of the metal-containing raw materials and the solvent.

[0080] The amount of each raw material added is preferably such that the catalyst has the composition described above. The composition of the catalyst is substantially equal to the amount (in terms of metal moles) of each raw material added (the composition of the catalyst is controlled by the amount (in terms of metal moles) of each raw material added). The mixing ratio of the Co-containing raw material and the Ni-containing raw material in solution A is preferably such that the composition described above is obtained. Similarly, the mixing ratio of the Fe-containing raw material and the Bi-containing raw material in solution B is preferably such that the composition described above is obtained.

[0081] The solvents used to prepare the above solutions A to D are the same as those described above (Fe ２ Mo ｘ O ｙ The same solvents as those described in the preparation of the precursor can be used. The solvents used to prepare solutions A to D may be the same or different, but are preferably the same.

[0082] A compound having an NH structure is added to at least one of solutions A to D. Here, as in the examples of WO 2010 / 038677, when the starting material mixture is evaporated to dryness and then ammonium nitrate (a compound having an NH structure according to the present invention) is added, the specific Fe as defined in the present invention can be obtained. ２ Mo ｘ O ｙ / ZnO peak intensity ratio (Comparative Example 7 below).

[0083] Here, the compound having an NH structure includes the above-mentioned (Fe ２ Mo ｘ O ｙ The same compounds as those described in the above (Preparation of Precursor) can be used. The amount of the compound having an NH structure added can be the same as that described above (Fe ２ Mo ｘ O ｙ The amount may be the same as that described in the previous section (preparation of the precursor).

[0084] The compound having an NH structure may be added to a solution prepared by adding each raw material to a solvent all at once, but it is preferable to add the compound having an NH structure to at least one of the above solutions A to D to obtain an Fe—Mo-containing suspension. It is more preferable to add the compound having an NH structure to the above solution A, B, or C. After adding the compound having an NH structure to the above solution A, B, or C, the remaining solutions are added together or sequentially, or it is even more preferable to add solution B and solution C to the above solution A to obtain a mixed solution, and then add the compound having an NH structure to the mixed solution. This makes it easier for the compound having an NH structure to associate with Fe or Mo, and specific Fe ２ Mo ｘ O ｙ Advantageously, a catalyst having a peak intensity ratio of ZnO / ZnO can be formed.

[0085] The above-mentioned addition operation may be carried out under stirring and / or heating. When the above-mentioned operation is carried out under stirring and / or heating, the temperature and / or time are not particularly limited and can be appropriately selected depending on the type of compound having an NH structure. Specifically, the above-mentioned (Fe ２ Mo ｘ O ｙ The same temperature and / or time as that for stirring the Fe—Mo-containing suspension described in the section (Preparation of Precursor) can be applied.

[0086] The dried product may be subjected to pulverization and / or classification as necessary to adjust the particle size to a suitable value. The particle size is not particularly limited, but is preferably, for example, a particle size such that 90% by mass or more of the total powder passes through a sieve with a mesh size of 500 μm, and more preferably, a particle size such that 90% by mass or more of the total powder passes through a sieve with a mesh size of 400 μm.

[0087] (Molding step) A catalyst precursor is obtained as described above. This catalyst precursor is molded or supported on a carrier to obtain a molded body (unsupported catalyst) or a supported body (supported catalyst). When molding the catalyst precursor, the catalyst precursor may be molded into a specific shape by a known molding method such as extrusion molding or tableting. The shape of the molded body is not particularly limited, and examples include spherical, cylindrical, ring-shaped, saddle-shaped, and irregular shapes. When the catalyst precursor is supported on a carrier, the catalyst precursor may be supported on any carrier having a specific shape to obtain a supported body. The material and shape of the carrier used to support the catalyst precursor are as described above.

[0088] When molding or supporting the catalyst precursor, a binder may be added to the catalyst precursor to improve the moldability or supportability of the catalyst precursor. Specific examples of binders include organic compounds such as ethylene glycol, glycerin, propionic acid, maleic acid, benzyl alcohol, propyl alcohol, butyl alcohol, phenols, celluloses (e.g., cellulose and ethyl cellulose), water, nitric acid, ammonium nitrate, and ammonium carbonate. A single binder may be used, or two or more binders may be used in combination. The binder may be added in its pure form or in the form of a solution (e.g., an aqueous solution). When a binder is used, for example, in the case of a support, the binder is added after the support is added.

[0089] Instead of or in addition to the above, a reinforcing material can be used to improve the mechanical strength of the catalyst. Specific examples of reinforcing materials include silica, alumina, ceramic fiber, glass fiber, carbon fiber, mineral fiber, metal fiber, and various whiskers such as silicon carbide and silicon nitride. The crystalline structure of the reinforcing material may be polycrystalline, monocrystalline, or amorphous, with polycrystalline or monocrystalline being preferred. Furthermore, multiple reinforcing materials with different fiber diameters, fiber lengths, materials, etc. may be used depending on the shape of the catalyst and the desired mechanical strength. The reinforcing material may be added to the raw material mixture or may be blended with the catalyst precursor during molding or loading. The reinforcing material may be used alone or in combination of two or more.

[0090] There are no particular limitations on the method for supporting the catalyst precursor on the carrier, and any conventionally known method can be used, such as a method using a tumbling granulator, the centrifugal fluid coating method described in JP-A-63-200839, or the rocking mixer method described in JP-A-2004-136267.

[0091] (Step of drying the supported granules) After the catalyst precursor has been supported on the carrier as described above, drying may be carried out. The supported granules (catalyst precursor supported on the carrier) may be dried by heating in a stream of air, an inert gas such as nitrogen, a nitrogen oxide, or a mixed gas thereof using a commonly used box dryer, tunnel dryer, or the like. The drying temperature is preferably 80 to 300°C, more preferably 130 to 250°C, and the drying time is preferably 1 to 20 hours.

[0092] (Calibration Step) A catalyst is obtained by calcining the dried product after the drying step or the supported granules after the drying step. Here, it is important to set the calcination temperature within an appropriate range in order to improve the yield of acrolein and / or acrylic acid. The calcination temperature is less than 510°C, preferably less than 505°C, more preferably 495°C or less, and particularly preferably 490°C or less. When the calcination temperature is 510°C or more, β-CoMoO ４ / α-Bi ２ Mo ３ O １２ The peak intensity ratio is high (β-CoMoO ４ Excessive crystals of α-Bi are formed. ２ Mo ３ O １２ Oxygen consumption and β-CoMoO ４ This is undesirable because it disrupts the balance of oxygen compensation by oxygen and reduces the yield. The lower limit of the calcination temperature is not particularly limited, but may be, for example, 250° C. or higher, 280° C. or higher, or 300° C. or higher. The calcination time may be 0.5 to 12 hours, or 1 to 10 hours.

[0093] The atmosphere for calcination is not particularly limited, and may be appropriately selected depending on the composition of the catalytically active component. Specifically, calcination can be carried out in an inert gas atmosphere such as nitrogen or argon, a reducing gas atmosphere such as hydrogen, or an oxygen-containing gas atmosphere such as air. Of these, the oxygen-containing gas atmosphere is preferred. The oxygen concentration in this atmosphere is preferably 1% by volume or more and 21% by volume or less.

[0094] [Production of acrolein and / or acrylic acid] By the above method, Fe ２ Mo ｘ O ｙ The composite oxide is mixed with a predetermined Fe ２ Mo ｘ O ｙ A catalyst containing propylene and acrylic acid having a peak intensity ratio of 0.1 to 0.1 / ZnO is obtained. This catalyst is particularly suitable for use in the first-stage reaction of producing acrolein from propylene in the production of acrylic acid by two-stage gas-phase oxidation, in which acrolein is obtained by catalytic gas-phase oxidation of propylene and then acrylic acid is obtained by catalytic gas-phase oxidation of the acrolein obtained. This improves the conversion rate of propylene, and as a result, acrolein and / or acrylic acid can be produced in high yield. Therefore, the catalyst according to the present invention is particularly suitable for use as a catalyst for producing acrolein and / or acrylic acid, particularly acrolein.

[0095] Therefore, in yet another aspect of the present invention, there is provided a method for producing acrolein and / or acrylic acid by catalytic gas-phase oxidation of propylene with a molecular oxygen-containing gas, the method comprising a step of carrying out catalytic gas-phase oxidation in the presence of the catalyst according to the present invention.

[0096] Hereinafter, one embodiment of a method for producing acrolein and / or acrylic acid using the catalyst according to the present invention or the catalyst produced above will be described.

[0097] The catalyst according to the present invention is packed into a reaction tube in a reactor, and a raw material gas containing propylene and molecular oxygen is introduced into the reaction tube to carry out a catalytic gas phase oxidation reaction, thereby producing acrolein and / or acrylic acid. A fixed-bed multi-tubular reactor, a plate reactor, or the like can be used as the reactor, with a fixed-bed multi-tubular reactor being more preferred. The inner diameter of the reaction tube in the fixed-bed multi-tubular reactor is typically 15 to 50 mm, more preferably 20 to 40 mm, and even more preferably 22 to 38 mm.

[0098] As long as the catalyst according to the present invention is packed into the reaction tube, the catalyst to be packed does not necessarily have to be a single catalyst, and it is also possible to pack a plurality of known catalysts so that each of them forms a layer (catalyst layer). For example, a method of packing catalysts with different loading rates so that the loading rate increases from the inlet side to the outlet side of the raw material gas, a method of diluting a part of the catalyst with an inert carrier or the like, or a combination of these methods may be adopted.

[0099] The raw material gas flowing through the reaction tube is a mixed gas consisting of preferably 1 to 15 vol%, more preferably 4 to 12 vol% propylene; preferably 0.5 to 25 vol%, more preferably 2 to 20 vol% molecular oxygen; preferably 0 to 35 vol%, more preferably 0 to 30 vol% water vapor; and the remainder an inert gas such as nitrogen. The mixture is heated at a temperature of 250 to 450°C under a pressure of 0.1 to 1.0 MPa for 300 to 5,000 hours. －１ The catalyst may be brought into contact with the fuel at a space velocity (standard condition).

[0100] There are no particular limitations on the grade of propylene used as the raw material gas, and polymer-grade or chemical-grade propylene can be used. A propylene-containing mixed gas obtained by the oxidative dehydrogenation reaction of propane can also be used, and air or oxygen can be added to this mixed gas as necessary.

[0101] By using the catalyst of the present invention, a high propylene conversion rate and a high acrolein and / or acrylic acid yield can be achieved. Specifically, a propylene conversion rate of 96.9 mol % or more, 97.0 mol % or more, and particularly 97.5 mol % or more can be achieved. Furthermore, an acrolein and / or acrylic acid yield of 91.7 mol % or more, 92.0 mol % or more, and particularly 92.2 mol % or more can be achieved.

[0102] Although embodiments of the present invention have been described in detail, they are illustrative or exemplary and not restrictive.

[0103] The present invention encompasses the following aspects and configurations.

[0104] 1. A catalyst for producing acrolein and / or acrylic acid by catalytic gas-phase oxidation of propylene in the presence of molecular oxygen or a molecular oxygen-containing gas, comprising Fe ２ Mo ｘ O ｙ The composite oxide contains a compound oxide, wherein x is 1.0 to 5.0 and y is 5.0 to 20.0, and in an X-ray diffraction analysis using ZnO as an internal standard, the ratio of the intensity of the maximum peak among the peaks attributable to ZnO at 2θ = 34.2 to 34.6° to the intensity of Fe at 2θ = 19.5 to 22.5° is ２ Mo ｘ O ｙ 1. A catalyst for producing acrolein and / or acrylic acid, in which the ratio of the maximum peak intensity among peaks attributed to the composite oxide exceeds 0.23; 2. In the catalyst described in 1. above, the molar ratio of molybdenum to iron (Mo / Fe) is preferably 4.2 to 16.4; 3. In the catalyst described in 1. or 2. above, ２ Mo ｘ O ｙ / ZnO) / (Fe / Mo)[Fe ２ Mo ｘ O ｙ / ZnO is the ratio of the intensity of the maximum peak among the peaks attributed to ZnO at 2θ=34.2 to 34.6° to the intensity of Fe at 2θ=19.5 to 22.5° in X-ray diffraction analysis using ZnO as an internal standard. ２ Mo ｘO ｙ Fe / Mo is the molar ratio of iron to molybdenum. ２ Mo ｘ O ｙ / ZnO peak intensity ratio is preferably 2.15 to 10.0; 4. The catalyst according to any one of the above items 1 to 3 preferably further contains cobalt; 5. The catalyst according to the above item 4 preferably contains β-CoMoO ４ In the X-ray diffraction analysis, β-CoMoO ４ The intensity of the maximum peak among the peaks assigned to Fe at 2θ = 19.5 to 22.5° ２ Mo ｘ O ｙ It is preferable that the ratio of the maximum peak intensity among the peaks attributed to the composite oxide exceeds 0.07; 6. In the catalyst described in 4. or 5. above, the molar ratio of molybdenum to cobalt (Mo / Co) is 1.05 or more; 7. In the catalyst described in any one of 4. to 6. above, the α-CoMoO ４ In the X-ray diffraction analysis, α-CoMoO ４ The intensity of the maximum peak among the peaks assigned to Fe at 2θ = 19.5 to 22.5° ２ Mo ｘ O ｙ It is preferable that the ratio of the maximum peak intensity among the peaks attributed to the composite oxide is 0.49 or more; 8. In the catalyst described in any one of the above items 4 to 7, the molar ratio of cobalt to iron (Co / Fe) is 1.1 to 10.3; 9. It is preferable that the catalyst described in any one of the above items 1 to 8 further contains bismuth; 10. The catalyst described in the above item 9 contains α-Bi ２ Mo ３ O １２ In the X-ray diffraction analysis, α-Bi at 2θ=27.7 to 28.1° is ２ Mo ３ O １２Fe at 2θ = 19.5 to 22.5° relative to the intensity of the maximum peak among the peaks assigned to ２ Mo ｘ O ｙ The ratio of the maximum peak intensity among the peaks attributed to the composite oxide (Fe ２ Mo ｘ O ｙ / α-Bi ２ Mo ３ O １２ 11. In the catalyst described in 9. or 10. above, the molar ratio of molybdenum to bismuth (Mo / Bi) is preferably 3.3 or more; 12. In the catalyst described in any one of 9. to 11. above, the molar ratio of bismuth to iron (Bi / Fe) is preferably 0.2 to 2.9; 13. The catalyst described in any one of 1. to 12. above further contains cobalt and bismuth, and in the X-ray diffraction analysis, the α-Bi ２ Mo ３ O １２ The intensity of the maximum peak among the peaks assigned to β-CoMoO at 2θ = 26.3 to 26.7° ４ The ratio of the maximum peak intensity among the peaks attributed to (β-CoMoO ４ / α-Bi ２ Mo ３ O １２ 14. The catalyst according to any one of the above 1. to 13. preferably further contains cobalt and bismuth, and preferably contains 4.2 to 16.4 mol of Mo, 0.2 to 2.9 mol of Bi, and 1.1 to 10.3 mol of Co per mol of Fe; 15. The catalyst according to any one of the above 1. to 14. preferably contains a cation exchange reaction product of Formula 2: Fe １ Mo ａ Bi ｂ Co ｃ Ni ｄ X ｅ O ｆ(In Formula 2, Fe is iron; Mo is molybdenum; Bi is bismuth; Co is cobalt; Ni is nickel; X is at least one element selected from the group consisting of vanadium (V), tungsten (W), antimony (Sb), cerium (Ce), titanium (Ti), manganese (Mn), potassium (K), germanium (Ge), chromium (Cr), sodium (Na), rubidium (Rb), cesium (Cs), and lithium (Li); a is the atomic ratio of Mo to one Fe atom and is 4.2 to 16.4; b is the atomic ratio of Bi to one Fe atom and is 0.2 to 2.9; c is the atomic ratio of Co to one Fe atom and is 1.1 to 10.3; d is the atomic ratio of Ni to one Fe atom and is 0.2 to 5.0; and e is the atomic ratio of Fe to one Fe atom and is 0.2 to 5.0. 16. The catalyst according to any one of 1. to 15. above preferably contains an oxide expressed by the formula: (where X is the atomic ratio of X to 1 atom, and is 0.01 to 0.30; and f is a value determined by the oxidation state of each element); ２ Mo ｘ O ｙ17. A method for producing a catalyst for producing acrolein and / or acrylic acid according to any one of 1. to 16. above, which comprises adding a compound having an NH structure to a solution containing a molybdenum-containing raw material and an iron-containing raw material, followed by calcining; 18. In the method according to 17. above, the compound having an NH structure is preferably at least one selected from the group consisting of ammonium acetate, ammonia, ammonium carbonate, melamine, ammonium nitrate, urea, cyanuric acid, ammonium chloride, ammonium hydrogencarbonate, ammonium oxalate, melamine cyanurate, methylamine, dimethylamine, ethylamine, diethylamine, allylamine, diallylamine, and aniline; 19. The method according to 17. or 18. above. 20. In the method described in any one of 17. to 19., it is preferable to add the compound having an NH structure so that the number of NH structures per mole of the molybdenum-containing raw material (calculated as molybdenum) is 0.01 to 1.00 mol and the number of NH structures per mole of the iron-containing raw material (calculated as iron) is 0.50 to 6.9 mol; 20. In the method described in any one of 17. to 19. above, it is preferable to carry out the calcination at a temperature of less than 510°C; 21. A method for producing acrolein and / or acrylic acid, comprising catalytically oxidizing propylene in the presence of molecular oxygen or a molecular oxygen-containing gas in the presence of the catalyst described in any one of 1. to 16. above.

[0105] The effects of the present invention will be explained using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples, and examples obtained by appropriately combining the technical means disclosed in each example are also included in the scope of the present invention. In the following examples, unless otherwise specified, operations were performed at 25°C. Furthermore, unless otherwise specified, "parts" means "parts by mass."

[0106] Example 1 Cobalt (II) nitrate hexahydrate (Co(NO)) was added to obtain the composition of catalyst A in Table 1. ３ ) ２ ・6H ２ 327 g of nickel(II) nitrate hexahydrate (Ni(NO)３ ) ２ ・6H ２ Solution A was obtained by dissolving 57 g of the compound O in 400 g of ion-exchanged water.

[0107] Iron (III) nitrate nonahydrate (Fe(NO)) was added to obtain the composition of catalyst A in Table 1. ３ ) ３ ・9H ２ 111 g of bismuth(III) nitrate pentahydrate (Bi(NO) ３ ) ３ ・5H ２ Solution B was obtained by dissolving 172 g of nitric acid in an aqueous solution of nitric acid composed of 65 g of a 65% by mass aqueous solution of nitric acid and 300 g of ion-exchanged water.

[0108] To obtain the composition of catalyst A in Table 1, ammonium paramolybdate (VI) tetrahydrate ((NH ４ ) ６ {Mo (Mo ６ O ２４ )・4H ２ 400 g of the compound O) was added to 1500 g of ion-exchanged water and dissolved with stirring to obtain a solution C.

[0109] To obtain the composition of catalyst A in Table 1, 1.4 g of potassium nitrate was dissolved in 30 g of ion-exchanged water to obtain solution D.

[0110] Liquids B and C were added to Liquid A, and the mixture was stirred and mixed for 3 hours while maintaining the temperature at 40°C, to obtain a mixed liquid. 53.1 g of ammonium acetate at 25°C was added to this mixed liquid, and then Liquid D was added to obtain a suspension. The obtained suspension was evaporated to dryness at 150°C for 5 hours to obtain a cake-like solid. This solid was dried in a tunnel dryer at 190°C for 9 hours and then pulverized to 400 μm or less to obtain a powdered catalyst precursor a.

[0111] 300 g of alumina spherical carriers with an average particle size of 5.0 mm were loaded into a tumbling granulator, followed by gradually loading 430 g of catalyst precursor a along with 145 g of a 25% by mass aqueous ammonium nitrate solution as a binder, thereby supporting the catalyst precursor on the alumina spherical carrier. The supported catalyst precursor was then dried in a tunnel dryer at 200°C for 3 hours under an air atmosphere. It was then calcined in a tunnel calcination furnace at 470°C for 6 hours under an air atmosphere to obtain catalyst A having the composition shown in Table 1. The resulting catalyst A was separated into catalyst components and carrier components using the method described above in [Separation of catalyst components from supported catalyst for measuring loading rate], and the catalyst loading rate was calculated using Equation 3 above. The loading rate of catalyst A was 120% by mass.

[0112] Examples 2 and 3 Catalysts B to C were obtained in the same manner as in Example 1, except that the amount of ammonium acetate added was changed to an amount corresponding to the composition shown in Table 1.

[0113] Comparative Example 1 Catalyst D was obtained in the same manner as in Example 1, except that ammonium acetate was not added.

[0114] Example 4 Catalyst E was obtained in the same manner as in Example 1, except that a 28% by mass aqueous ammonia solution was added in place of ammonium acetate so as to obtain the composition of catalyst E shown in Table 1.

[0115] Comparative Example 2 Catalyst F was obtained in the same manner as in Example 1, except that citric acid was added in place of ammonium acetate so as to obtain the composition of catalyst F shown in Table 1.

[0116] Example 5 Catalyst G was obtained in the same manner as in Example 1, except that ammonium carbonate was used in place of ammonium acetate so as to obtain the composition of catalyst G shown in Table 1.

[0117] Example 6 Catalyst H was obtained in the same manner as in Example 1, except that melamine was used in place of ammonium acetate so as to obtain the composition of catalyst H shown in Table 1.

[0118] Comparative Example 3 Catalyst I was obtained in the same manner as in Example 5, except that ammonium carbonate was not added so that the composition of Catalyst I in Table 1 was obtained.

[0119] Example 7 Catalyst J was obtained in the same manner as in Example 1, except that ammonium nitrate was used in place of ammonium acetate so as to obtain the composition of catalyst J shown in Table 1.

[0120] Example 8 Catalyst K was obtained in the same manner as in Example 1, except that urea was used in place of ammonium acetate so as to obtain the composition of catalyst K shown in Table 1.

[0121] Example 9 Catalyst L was obtained in the same manner as in Example 1, except that cyanuric acid was used in place of ammonium acetate so as to obtain the composition of catalyst L shown in Table 1.

[0122] Comparative Example 4 Catalyst M was obtained in the same manner as in Example 7, except that ammonium nitrate was not added, so that the composition of catalyst M in Table 1 was obtained.

[0123] Example 10 Catalyst N was obtained in the same manner as in Example 1, except that the amount of iron (III) nitrate nonahydrate was changed so as to obtain the composition of Catalyst N shown in Table 1.

[0124] Example 11 Catalyst O was obtained in the same manner as in Example 1, except that the amount of iron (III) nitrate nonahydrate was changed so as to obtain the composition of catalyst O shown in Table 1.

[0125] Comparative Example 5 Catalyst P was obtained in the same manner as in Example 1, except that the amount of iron (III) nitrate nonahydrate was changed so as to obtain the composition of catalyst P shown in Table 1.

[0126] Comparative Example 6 Catalyst Q was obtained in the same manner as in Example 1, except that the amount of ammonium paramolybdate (VI) tetrahydrate was changed so as to obtain the composition of Catalyst Q shown in Table 1.

[0127] Comparative Example 7 A catalyst precursor powder r was obtained in the same manner as in Example 3, except that ammonium acetate was not added so that the composition of catalyst R in Table 1 was obtained.

[0128] After adding 21.3 g of ammonium acetate to the powder r obtained above, 300 g of alumina spherical carriers with an average particle size of 5.0 mm were placed in a tumbling granulator, and then the powder r was gradually added together with a 25% by mass aqueous solution of ammonium nitrate as a binder, thereby supporting the powder r on the alumina spherical carrier. Next, the mixture was calcined in an air atmosphere at 470°C for 6 hours to obtain catalyst R.

[0129] Example 12 Catalyst S was obtained in the same manner as in Example 1, except that in Example 3, the catalyst was calcined at 510° C. for 4 hours in an air atmosphere so as to have the composition of catalyst S shown in Table 1.

[0130] The total Fe ions (Fe ３＋ +Fe ２＋ ) to Fe ３＋ The molar ratio (Fe ３＋ / (Fe ３＋ +Fe ２＋ ) was measured and found to be 0.9 or more.

[0131] The compositions of the obtained catalysts A to S (molar ratios of molybdenum, bismuth, cobalt, nickel, and potassium per mole of iron), as well as the types of compounds having an NH structure added during the production of each catalyst and the amounts (moles) added per mole of iron are shown in Table 1 below.

[0132] Table 2 also lists the type of compound having an NH structure added during the production of each of the resulting catalysts A to S, the loading rate, the molar ratio of iron per mole of molybdenum ("Fe / Mo" in Table 2 below), the molar ratio of molybdenum per mole of bismuth ("Mo / Bi" in Table 2 below), the molar ratio of molybdenum per mole of cobalt ("Mo / Co" in Table 2 below), the number of NH structures per mole of molybdenum ("Number of NH structures / Mo" in Table 2 below), and the number of N groups (moles) in the NH structure.

[0133]

[0134]

[0135] [X-ray diffraction analysis] For the catalyst components separated from the carriers of the catalysts A to S obtained above by the method described above, samples containing a powdered internal standard were prepared by the method described above in [X-ray diffraction analysis using ZnO as an internal standard] using 0.1 g of ZnO (manufactured by Kanto Chemical Co., Inc., purity >99.0%, wurtzite structure) as an internal standard per 1 g of catalyst component under the following conditions. Next, the prepared sample containing ZnO as an internal standard was subjected to X-ray diffraction analysis under the following conditions.

[0136] (X-ray diffraction conditions) X-ray diffraction analyzer: Aeris manufactured by Spectris Co., Ltd., Malvern Panalytical Division X-ray source: CuKα ray (λ=0.154 nm) Applied voltage: 40 kV Applied current: 15 mA Measurement change angle: 2θ Measurement speed: 0.1358° / min Measurement speed range: 5° to 90° Analysis step width: 0.0108° The obtained X-ray diffraction pattern was analyzed using analysis software (HighScore Plus) attached to the X-ray diffraction analyzer. ４ peak, Fe at 19.5-22.5° ２ Mo ｘ O ｙ Complex oxide peak, Fe at 21.3-21.8° ２ Mo ３ O １２ β-CoMoO peak at 26.3-26.7° ４ α-Bi at 27.7-28.1° ２ Mo ３ O １２ The presence of a peak of ZnO at 34.2 to 34.6° was confirmed. The intensity ratios shown in Table 3 were obtained from the intensities of the maximum peaks at predetermined diffraction angles for each of these composite oxides. The results are shown in Table 3 below.

[0137]

[0138] [Performance Evaluation] For the catalysts A to S obtained above, propylene was catalytically oxidized in the presence of molecular oxygen or a molecular oxygen-containing gas according to the following method, and the propylene conversion and the yields of acrolein and acrylic acid were measured.

[0139] A reactor was prepared vertically, consisting of a stainless steel reaction tube with a total length of 3000 mm and an inner diameter of 25 mm, and a shell surrounding the reaction tube for passing a heat transfer medium. Each catalyst was dropped from the top of the reaction tube to fill the reactor so that the bed length was 2600 mm.

[0140] Next, the heat transfer medium temperature (reaction temperature) was kept at 310°C, and a mixed gas consisting of 6% by volume of propylene, 11% by volume of oxygen, 15% by volume of steam, and the remainder of nitrogen gas was introduced from the bottom of the reaction tube filled with the catalyst at a space velocity of 1500 h －１ (standard conditions). The amount of propylene remaining after the reaction, the amount of acrolein produced, and the amount of acrylic acid produced were measured by gas chromatography. The number of moles of propylene consumed in the reaction was calculated from the amount of propylene supplied and the amount of propylene remaining after the reaction.

[0141] Based on these values, the propylene conversion, the acrolein yield, and the total yield of acrylic acid were calculated according to the following formulas. The results are shown in Table 4.

[0142] (Conditions for measuring the amounts of propylene, acrolein, and acrylic acid) Analytical equipment: GC-8A and GC-2010 manufactured by Shimadzu Corporation Columns: Molecular Sieve 5A, Shincarbon-ST 50 / 80, and ULBON HR-20M 0.53 mm ID × 30 m 3.0 μm Detectors: TCD and FID

[0143]

[0144]

[0145] From Table 4 above, it can be seen that the catalysts of the examples have significantly higher propylene conversion rates and higher acrolein and acrylic acid yields than the catalysts of the comparative examples.

[0146] This application is based on Japanese Patent Application No. 2024-121182, filed on July 26, 2024, the disclosure of which is hereby incorporated by reference in its entirety.

Claims

1. A catalyst for producing acrolein and / or acrylic acid by catalytic gas-phase oxidation of propylene in the presence of molecular oxygen or a molecular oxygen-containing gas, comprising Fe ２ Mo ｘ O ｙ The composite oxide contains a compound oxide, wherein x is 1.0 to 5.0 and y is 5.0 to 20.0, and in an X-ray diffraction analysis using ZnO as an internal standard, the ratio of the intensity of the maximum peak among the peaks attributable to ZnO at 2θ = 34.2 to 34.6° to the intensity of Fe at 2θ = 19.5 to 22.5° is ２ Mo ｘ O ｙ A catalyst for producing acrolein and / or acrylic acid, in which the ratio of the maximum peak intensity among the peaks assigned to 2. The catalyst for producing acrolein and / or acrylic acid according to claim 1, further comprising cobalt.

3. β-CoMoO ４ In the X-ray diffraction analysis, β-CoMoO ４ The intensity of the maximum peak among the peaks assigned to Fe at 2θ = 19.5 to 22.5° ２ Mo ｘ O ｙ 3. The catalyst for producing acrolein and / or acrylic acid according to claim 2, wherein the ratio of the intensity of the maximum peak among the peaks assigned to 4. The catalyst for producing acrolein and / or acrylic acid according to claim 2, wherein the molar ratio of molybdenum to cobalt (Mo / Co) is 1.05 or more.

5. The catalyst for producing acrolein and / or acrylic acid according to claim 1, further comprising bismuth. 6.α-Bi ２ Mo ３ O １２ and wherein, in the X-ray diffraction analysis, α-Bi is ２ Mo ３ O １２ The intensity of the maximum peak among the peaks assigned to Fe at 2θ = 19.5 to 22.5° ２ Mo ｘ O ｙ 6. The catalyst for producing acrolein and / or acrylic acid according to claim 5, wherein the ratio of the intensity of the maximum peak among the peaks assigned to 7. The catalyst for producing acrolein and / or acrylic acid according to claim 5, wherein the molar ratio of molybdenum to bismuth (Mo / Bi) is 3.3 or more.

8. α-CoMoO ４ and in the X-ray diffraction analysis, at 2θ=13.9 to 14.3°, the ４ The intensity of the maximum peak among the peaks assigned to Fe at 2θ = 19.5 to 22.5° ２ Mo ｘ O ｙ 3. The catalyst for producing acrolein and / or acrylic acid according to claim 2, wherein the ratio of the intensity of the maximum peak among the peaks attributed to 9. The catalyst for producing acrolein and / or acrylic acid according to claim 1, which contains 4.2 to 16.4 mol of Mo, 0.2 to 2.9 mol of Bi, and 1.1 to 10.3 mol of Co per mol of Fe.

10. β-CoMoO ４ and α-Bi ２ Mo ３ O １２ In the X-ray diffraction analysis, α-Bi at 2θ=27.7 to 28.1° is ２ Mo ３ O １２ The intensity of the maximum peak among the peaks assigned to β-CoMoO at 2θ = 26.3 to 26.7° ４ 2. The catalyst for producing acrolein and / or acrylic acid according to claim 1, wherein the ratio of the intensity of the maximum peak among the peaks assigned to 11. Molar ratio gradient distribution Fe shown in the following formula 1 ２ Mo ｘ O ｙ The catalyst for producing acrolein and / or acrylic acid according to claim 1, wherein the peak intensity ratio of ZnO to ZnO is 2.15 to 10.

0. In the above formula 1, Fe ２ Mo ｘ O ｙ / ZnO is the ratio of the intensity of the maximum peak among the peaks attributed to ZnO at 2θ=34.2 to 34.6° to the intensity of Fe at 2θ=19.5 to 22.5° in X-ray diffraction analysis using ZnO as an internal standard. ２ Mo ｘ O ｙ and Fe / Mo is the molar ratio of iron to molybdenum.

12. A method for producing the catalyst for producing acrolein and / or acrylic acid according to any one of claims 1 to 11, comprising adding a compound having an NH structure to a solution containing a molybdenum-containing raw material and an iron-containing raw material, followed by calcination.

13. The method according to claim 12, wherein the compound having an NH structure is at least one selected from the group consisting of ammonium acetate, ammonia, ammonium carbonate, melamine, ammonium nitrate, urea, cyanuric acid, ammonium chloride, ammonium hydrogen carbonate, ammonium oxalate, melamine cyanurate, methylamine, dimethylamine, ethylamine, diethylamine, allylamine, diallylamine, and aniline.

14. The method according to claim 12, wherein the compound having an NH structure is added so that the number of NH structures per mole of the molybdenum-containing raw material (calculated as molybdenum) is 0.01 to 1.00 moles and the number of NH structures per mole of the iron-containing raw material (calculated as iron) is 0.50 to 6.9 moles.

15. A method for producing acrolein and / or acrylic acid, comprising catalytically oxidizing propylene in the presence of molecular oxygen or a molecular oxygen-containing gas in the presence of the catalyst according to any one of claims 1 to 11 to produce acrolein and / or acrylic acid.

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