JPH0710353B2 - Vanadium-phosphorus oxide-based oxidation catalyst and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a crystalline vanadium-phosphorus oxide-based oxidation catalyst having a novel structure and a method for producing the same. "Oxidation" of the oxidation catalyst used in the present invention means oxidation in a broad sense, and is used in a meaning including not only ordinary oxidation but also oxidative dehydrogenation and ammoxidation. More specifically, the present invention shows a previously unknown characteristic X-ray diffraction pattern, for example, by the production of maleic anhydride by butane oxidation, the production of methacrylic acid by oxidative dehydrogenation of isobutyric acid, or the oxidation of methacrolein. The present invention relates to a novel vanadium-phosphorus oxide-based oxidation catalyst suitable for the production of methacrylic acid or the production of cyanopyridine by ammoxidation of methylpyridine, and a process for producing the same. The reaction for which the catalyst of the present invention is used is an oxidation reaction in a broad sense for organic substances.

[0002]

2. Description of the Related Art Conventionally, there are composite oxides composed of vanadium and phosphorus, one having a phosphorus / vanadium atomic ratio of one and the other having a phosphorus / vanadium atomic ratio of 2, and VOPO ₄ having a vanadium valence of 5+. Many structural isomers such as (VO) ₂ P ₂ O ₇ and VO (PO ₃ ) ₂ in which vanadium has a valence of 4+ have been reported ( Surface , 20, 605 (198).
2); Catalyst today Vol. One, four
99 (1987)).

However, it is known that an oxide catalyst composed of vanadium and phosphorus is effective as a catalyst for the synthesis of maleic anhydride by the oxidation of butane (US Pat. No. 4).
043943, Dutch Patent 738517, etc.).
And, it has been reported that the active form of this catalyst is vanadium pyrophosphate ((VO) ₂ P ₂ O ₇ ) (Mizono, Bul. Chem. Soc. Japan, 58 ,
2063 (1985)). This (VO) ₂ P ₂ O ₇ can be identified from its characteristic X-ray diffraction pattern. The main peaks of the X-ray diffraction pattern of this (VO) ₂ P ₂ O ₇ are shown in Table 3 below. Table 3 [Main peak of (VO) ₂ P ₂ O ₇ : d (Å)] 6.28 W 3.87 VS 3.14 VS 2.99 M 2.44 M (However, in Table 3, VS is particularly Shows a strong peak intensity,
S indicates a strong peak intensity, M indicates a medium peak intensity, and W indicates a weak peak intensity. )

It has been reported that a mixed catalyst of vanadium pentoxide and phosphoric acid is effective for the synthesis of methacrylic acid by oxidative dehydrogenation of isobutyric acid or the oxidation of methacrolein. For the oxidative dehydrogenation of isobutyric acid, the phosphorus / vanadium atomic ratio is in the range of 1.0 to 1.6, and for the oxidation of methacrolein, the phosphorus / vanadium atomic ratio is
It has been reported that the vanadium atomic ratio of 1.06 is optimal (J. Catal., 98 , 401 (1
986); ibid. 116 , 23 (1989)).

For the ammoxidation reaction, for example, the ammoxidation of methylpyridine to cyanopyridine, α
It has been reported that-, β-VOPO ₄ , and (VO) ₂ P ₂ O ₇ are effective catalysts (Japanese Patent Laid-Open No. 63-72675).
issue). Both structural isomers of α- and β-VOPO ₄ can be identified by X-ray diffraction patterns, and the main peaks of the X-ray diffraction patterns of both structural isomers are shown in Table 4 below. Table 4 [Main peaks of α-, β-VOPO ₄ : d (Å)] α-VOPO ₄ β-VOPO ₄ 3.57 S 5.19 S 3.07 M 4.61 S 3.01 VS 3.39 VS 2.13 M 3.07 VS 1.90 S 2.09 VS (However, in Table 4, VS, S, and M indicate the strength of peak intensity as in the case of Table 3.)

Furthermore, as an example of a silica-supported vanadium-phosphorus oxide catalyst developed as a catalyst for the synthesis of maleic anhydride from butane by a fluidized bed catalytic oxidation reaction, a mixture of vanadyl oxalate solution, phosphoric acid and silica sol is used. Catalyst prepared by spray-drying
75), or vanadium pyrophosphate ((VO) ₂ P ₂ O ₇ ) which is an active substance, is applied to silica sol by using vanadium pentoxide dissolved in an aqueous solution of phosphoric acid and oxalic acid as a binder. (JP-A-58-170
No. 542) and the like are known.

However, the above-mentioned conventionally known vanadium-phosphorus oxide catalysts have problems in terms of activity, physical properties such as strength and fluidity, and their preparation is difficult. It is too complicated and not a satisfactory catalyst.

[0008]

Although various crystalline complex oxides are known as vanadium-phosphorus oxides as described above, many more unknown new structural isomers and nonstoichiometric oxidations are known. Although it is extremely difficult to investigate and prepare them systematically, they can be found and some of them have a high or specific catalytic function. It is possible that there is something that has. Therefore, in view of the fact that the conventionally known vanadium-phosphorus oxides are not yet satisfactory as described above, the present invention proposes the possibility of finding new structural isomers and nonstoichiometric oxides. In pursuit, a novel vanadium-phosphorus oxide-based oxidation catalyst having excellent catalytic activity and physical properties such as excellent strength and fluidity that can be suitably applied to, for example, a fluidized bed catalytic oxidation reaction system, and relatively The purpose is to provide it by an easy manufacturing method.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has found that among the water-soluble crystalline vanadium-phosphorus composite oxides, the phosphorus / vanadium atomic ratio is 1.0 to 1 When a vanadium-phosphorus oxide-based oxidation catalyst was prepared by using a water-soluble vanadium-phosphorus composite oxide showing a constant X-ray diffraction peak of 0.6 and silica sol as raw materials, it was found that a novel and specific X-ray The present invention has been completed by discovering that it exhibits a diffraction peak and has excellent catalytic activity for oxidation reaction and excellent physical properties such as strength.

Therefore, the gist of the first invention is phosphorus /
Water-soluble vanadium having a vanadium atomic ratio in the range of 1.0 to 1.6 and exhibiting an X-ray diffraction peak in Table 1 below.
It exists in a vanadium-phosphorus oxide-based oxidation catalyst that is prepared using phosphorus oxide and silica sol as raw materials and exhibits the characteristic X-ray diffraction peaks in Table 2 below.

The gist of the second invention is that the phosphorus / vanadium atomic ratio is in the range of 1.0 to 1.6, and X in Table 1 below.
1 of a slurry prepared by mixing an aqueous solution of water-soluble vanadium-phosphorus oxide showing a line diffraction peak and silica sol
The method for producing a vanadium-phosphorus oxide-based oxidation catalyst according to the gist of the first aspect of the invention is characterized by drying at 00 to 250 ° C. Table 1 [X-ray diffraction peak of water-soluble vanadium-phosphorus oxide: d (Å)] 4.90 to 4.70 M to W 4.25 to 4.10 VS to S 3.20 to 3.10 M 2.75 to 2.65 M to W 2.50 to 2.35 M to W Table 2 [X-ray diffraction peak of vanadium-phosphorus oxide catalyst: d (Å)] 7.18 ± 0.02 VS 3. 59 ± 0.01 S to M 3.10 ± 0.01 M 3.05 ± 0.01 S to M 2.36 ± 0.02 W (In Table 1 and Table 2, VS is particularly strong peak intensity. , S indicates a strong peak intensity, M indicates a medium peak intensity, and W indicates a weak peak intensity.)

The water-soluble vanadium-phosphorus oxide (hereinafter referred to as "β'-phase") used as a raw material for preparation in the present invention
Is generally a pentavalent vanadium compound such as V ₂ O ₅ ,
After reducing VOCl ₃ , VO (NO ₃ ) ₃ or NH ₄ VO ₂ into a tetravalent vanadium compound with a reducing agent, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, phosphorus pentoxide, ethyl phosphate or It is obtained by reacting with methyl phosphate or the like, heat-treating the produced solid in air at 500 to 700 ° C., and again oxidizing tetravalent vanadium to pentavalent vanadium. The phosphorus / vanadium atomic ratio is 1.0 to
The range is 1.6, preferably 1.0 to 1.4, and more preferably 1.0 to 1.3. Further, as the reducing agent, hydroxylamine hydrochloride, hydrazines, aliphatic alcohols having 1 to 6 carbon atoms, 1 to 8 carbon atoms
Ordinary reducing agents such as aliphatic or aromatic aldehydes or hydrogen chloride may be used. The reduction treatment with a reducing agent such as V ₂ O ₅ is usually performed at a temperature near the boiling point when the reducing agent used is an organic substance, and at a temperature of tens of degrees even when the reducing agent used is not an organic substance such as hydrogen chloride. The subsequent reaction with the orthophosphoric acid or the like is usually carried out at the same temperature as in the reduction treatment.

The existence of the β'-phase described here is
Inventors of the present invention in Chem. Lette
rs, 1897 (1987).

In the catalyst of the present invention, the β'-phase obtained as described above is made into an aqueous solution, and the aqueous solution and silica sol are mixed to form a slurry, and the slurry is 100 to 250 ° C.
It can be manufactured by drying with.

In the production of the catalyst of the present invention, even if the use of β'-phase showing a specific characteristic X-ray diffraction pattern as a raw material is specified as the raw material, the raw material can be used as long as it is supported as an aqueous solution on silica as a support. It may seem that there is no technical meaning to limit the crystal structure of β to the β′-phase showing a specific X-ray diffraction pattern. However, this limitation has important implications. That is, a large number of vanadium-phosphorus complex oxides among the water-soluble complex oxides are β′-phase, VOPO ₄ ·.
Based on the fact that there are only three kinds of H ₂ O and VO (H ₂ PO ₄ ) ₂ , and among them, only the β′-phase defined in the present invention shows the activity when supported on silica. There is.

In the production of the catalyst of the present invention, the mixing ratio of the β'-phase and the silica sol is preferably 95 to 20% by weight of the β'-phase and 5 to 80% by weight of the silica sol in terms of dry weight. Yes, preferably β'-phase 90-70% by weight
The silica sol is 10 to 30% by weight. Also,
Drying of the mixed slurry of β′-phase and silica sol can be performed by spray drying or any other means. Further, after drying the mixed slurry of β′-phase and silica sol, it may be further heat-treated at 100 to 250 ° C. if necessary. The catalyst thus obtained exhibits a characteristic X-ray diffraction peak as shown in Table 2 above.

All the X-ray diffraction peaks in Table 2 belong to the vanadium-phosphorus complex oxide which is the active component of the catalyst of the present invention, and the silica as the carrier is amorphous silica, and the X-ray diffraction peak Does not give a peak at. The X-ray diffraction pattern of Table 2 was obtained by Bordes in 1984, J. Am. S
ol. State Chem. , 55 , 270 (19
It was confirmed that it is a new, so-called γ'-phase, which is distinct from the γ-phase and distinct from the diffraction pattern of the γ-phase reported in 84). Has been done.

The X-ray diffraction pattern shown in the present invention uses the Kα ray of Cu as the anticathode, and its measurement accuracy is 2θ = ± 0.1 °.

The catalyst of the present invention can be used in any suitable form such as powder, column, sphere and the like depending on the purpose of use, and the reaction system can be any known one such as fluidized bed, fixed bed and moving bed. Operation is available.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to examples showing examples of the catalyst of the present invention and reference examples showing examples of reactions using the catalyst of the present invention. It is not limited to the above. Example 1 To 80 ml of ethanol was added 10 g of vanadium pentoxide to give 7
Stir while heating to 0 ° C., and add hydrogen chloride gas to this at 10
I understood for a minute. After heating for 4 hours, 12.4 g of 98 wt% orthophosphoric acid was added and the mixture was refluxed for 1 hour. Then, ethanol was evaporated and a solid was taken out. The phosphorus / vanadium atomic ratio in the solid was 1.1. 6 this solid
It heat-processed in the air at 00 degreeC for 4 hours. The X-ray diffraction peak of the solid after the heat treatment is as shown below, and it was confirmed that this solid was in the β'-phase. d (Å) Sign of peak strength 4.88 W 4.22 VS 3.19 M 2.72 M 2.44 W Here, the signs of VS, M, W, etc. are the same as above, and peak strength And the same shall apply hereafter.

10 g of the above solid (β'-phase) was added to 100 ml of distilled water, heated to 100 ° C., and stirred to dissolve. 10 g of silica sol (SiO 2 was added to the obtained reddish brown solution.
₍₂ concentration 20% by weight) was added and the mixture was evaporated to dryness at 120 ° C. with stirring. Then, heat treatment was performed at 200 ° C. for 4 hours. The weight ratio of vanadium-phosphorus oxide to silica in the obtained catalyst was 5: 1. Further, this catalyst gave an X-ray diffraction peak of the characteristic γ'-phase shown below. Sign of strength of d (Å) peak 7.17 VS 3.59 M 3.10 M 3.06 S 2.36 W

Example 2 10 g of vanadium pentoxide was added to 80 ml of isobutanol, and stirring was continued for 12 hours while heating at 80 ° C. Then, 12.4 g of 98 wt% orthophosphoric acid was added and refluxed for 1 hour. Then, isobutanol was removed by evaporation. The obtained solid was gradually heated up to 350 ° C., then kept at 350 ° C. for 4 hours, and further heat-treated in air at 600 ° C. for 4 hours. Phosphorus in the solid after this heat treatment
The vanadium atomic ratio was 1.1. The X-ray diffraction peak of the solid after the heat treatment was as shown below, and it was confirmed that the solid was in the β'-phase. Sign of strength of d (Å) peak 4.87 W 4.23 VS 3.20 M 2.71 M 2.44 W

10 g of the above solid (β'-phase) was added to 100 ml of distilled water, heated to 100 ° C., and dissolved by stirring. 10 g of silica sol (SiO 2 was added to the obtained reddish brown solution.
₍₂ concentration 20% by weight) was added and the mixture was evaporated to dryness at 120 ° C. with stirring. Then, heat treatment was performed at 200 ° C. for 4 hours. The weight ratio of vanadium-phosphorus oxide to silica in the obtained catalyst was 5: 1. Further, this catalyst gave an X-ray diffraction peak of the characteristic γ'-phase shown below. Sign of strength of d (Å) peak 7.19 VS 3.59 S 3.11 M 3.06 S 2.36 W

Example 3 To 200 ml of distilled water were added 14.3 g of hydroxylamine hydrochloride and 27.7 g of 85 wt% orthophosphoric acid, and the mixture was heated to 70 ° C. and dissolved. 18.4 g of vanadium pentoxide in this solution
Was added and heated with stirring for 3 hours to cause reaction, and then evaporated to dryness at 110 ° C. The obtained solid was gradually heated in air to 600 ° C. and heat-treated at 600 ° C. for 4 hours. The phosphorus / vanadium atomic ratio in the solid after this heat treatment was 1.2. Further, the X-ray diffraction peak of the solid after this heat treatment was as shown below, and it was confirmed that this solid was in the β'-phase. Sign of strength of d (Å) peak 4.72 M 4.12 S 3.15 M 2.70 W 2.40 W

10 g of the above solid (β'-phase) was added to 100 ml of distilled water, heated to 100 ° C., and stirred to dissolve. 10 g of silica sol (SiO 2 was added to the obtained reddish brown solution.
₍₂ concentration: 20% by weight) was added and spray-dried at 200 ° C. The weight ratio of vanadium-phosphorus oxide to silica in the obtained catalyst was 5: 1. Further, this catalyst gave an X-ray diffraction peak of the characteristic γ'-phase shown below. The sign of the intensity of the d (Å) peak 7.20 VS 3.59 S 3.10 M 3.05 M 2.36 W The X-ray diffraction measurement result of each catalyst obtained in each of the above examples is shown in FIG. .

Reference Example 1 (Synthesis of Maleic Anhydride by Butane Oxidation) Using an air mixed gas containing 2 mol% of butane and using a small flow reactor under normal pressure, SV 1000 hr ^{−1 based} on the mixed gas per catalyst volume. Each catalyst obtained in Examples 1 to 3 was brought into contact with each other, and the activity test of each catalyst was performed. The catalyst of the present invention survived a fluidized bed experiment for a long time, the loss of the catalyst was very small, and the change in conversion rate and yield with time were also slight. The reaction results are shown below. The conversion rate and the yield are on a molar basis, and the same applies to the following reference examples. Catalyst Reaction temperature Butane conversion rate Maleic anhydride yield (° C) (%) (%) Catalyst of Example 1 440 95 58 Catalyst of Example 2 460 100 59 Catalyst of Example 3 460 80 52

Reference Example 2 (Methacrylic Acid Synthesis by Methacrolein Oxidation) 3 g / min of methacrolein, 10 ml / min of oxygen, 20 ml / min of steam and 5 ml of each catalyst obtained in Examples 1 to 3 were used. Helium was passed through at a rate of 70 ml / min (mixed gas standard SV1200 hr ⁻¹ ) to carry out an activity test of each catalyst. The results are shown below. Catalyst Reaction temperature Methacrolein Methacrylic acid yield (° C.) Conversion (%) (%) Catalyst of Example 1 330 55 37 37 Catalyst of Example 2 310 51 32 Catalyst of Example 3 310 41 32

Reference Example 3 (Synthesis of methacrylic acid by oxidative dehydrogenation of isobutyric acid) On each 5 g of the catalysts obtained in Examples 1 to 3, isobutyric acid 3 ml / min, oxygen 6 ml / min, steam 3 ml / min. mi
80 ml / min of n and helium (mixed gas standard S
Each catalyst was tested for activity by passing V1100 hr ^-1 ). The results are shown below. Catalyst Reaction temperature Isobutyric acid conversion rate Methacrylic acid yield (° C) (%) (%) Catalyst of Example 1 300 100 62 Catalyst of Example 2 320 100 68 68 Catalyst of Example 3 320 90 52

Reference Example 4 (Synthesis of 4-cyanopyridine by ammoxidation of 4-methylpyridine) Onto 5 g of each of the catalysts obtained in Examples 1 to 4,
Cyanopyridine 3 ml / min, oxygen 6 ml / min, ammonia 18 ml / min, water vapor 18 ml / min and helium 60 ml / min (mixed gas standard SV1200 hr ^-1 )
Each catalyst was tested for activity. The results are shown below. Catalyst Reaction temperature 4-Cyanopyridine Methacrylic acid yield (° C.) Conversion (%) (%) Catalyst of Example 1 380 92 88 Catalyst of Example 2 380 94 88 Catalyst of Example 3 380 94 92

[0030]

According to the present invention, a novel vanadium-phosphorus oxide catalyst exhibiting a certain characteristic X-ray diffraction peak is obtained.
It is provided by a relatively easy manufacturing method. The vanadium-phosphorus oxide catalyst has excellent catalytic activity and physical properties such as excellent strength. For example, it is possible to produce maleic anhydride by fluidized bed oxidation of butane, oxidative dehydrogenation of isobutyric acid, or methacrolein oxidation. It is an extremely effective oxidation catalyst for production of methacrylic acid or production of cyanopyridine by ammoxidation of methylpyridine.

[Brief description of drawings]

FIG. 1 is a diagram showing an X-ray diffraction measurement result of each catalyst obtained in Examples 1 to 3.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C07D 307/60 B

Claims (3)

[Claims] 1. A phosphorus / vanadium atomic ratio of 1.0 to 1.
Vanadium-phosphorus having a range of 6 and a water-soluble vanadium-phosphorus oxide showing the X-ray diffraction peak of the following Table 1 and silica sol as raw materials, and showing the characteristic X-ray diffraction peak of the following Table 2 Oxide-based oxidation catalyst. Table 1 [X-ray diffraction peak of water-soluble vanadium-phosphorus oxide: d (Å)] 4.90 to 4.70 M to W 4.25 to 4.10 VS to S 3.20 to 3.10 M 2.75 to 2.65 M to W 2.50 to 2.35 M to W Table 2 [X-ray diffraction peak of vanadium-phosphorus oxide catalyst: d (Å)] 7.18 ± 0.02 VS 3. 59 ± 0.01 S to M 3.10 ± 0.01 M 3.05 ± 0.01 S to M 2.36 ± 0.02 W (In Table 1 and Table 2, VS is particularly strong peak intensity. , S indicates a strong peak intensity, M indicates a medium peak intensity, and W indicates a weak peak intensity.) 2. A phosphorus / vanadium atomic ratio of 1.0 to 1.
6, and a slurry prepared by mixing an aqueous solution of a water-soluble vanadium-phosphorus oxide showing an X-ray diffraction peak in Table 1 below and silica sol is dried at 100 to 250 ° C. The method for producing the vanadium-phosphorus oxide-based oxidation catalyst according to claim 1. Table 1 [X-ray diffraction peak of water-soluble vanadium-phosphorus oxide: d (Å)] 4.90 to 4.70 M to W 4.25 to 4.10 VS to S 3.20 to 3.10 M 2.75 to 2.65 M to W 2.50 to 2.35 M to W (However, in Table 1, VS indicates a particularly strong peak intensity,
S indicates a strong peak intensity, M indicates a medium peak intensity, and W indicates a weak peak intensity. ) 3. The mixing ratio of the water-soluble vanadium-phosphorus oxide and the silica sol is 95 to 20% by weight of the water-soluble vanadium-phosphorus oxide, and 5 to 80% by weight of the silica sol. The manufacturing method according to claim 2, which is a percentage.