JPH11226411A - Catalyst for production of methacrylic acid and production of methacrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a catalyst having high methacrylic acid selectivity and excellent in catalyst strength and to produce methacrylic acid with high selectivity by using the catalyst. SOLUTION: A powdery catalyst comprising a compsn. represented by the formula Moa Vb Pc Sd Xe Yf (NH4 )g Oh (where X is one or more elements selected from the group consisting of Sb, Si, Cu, Co, Bi and As and Y is one or more elements selected from the group consisting of K, Rb, Cs and Tl) is mixed with purified starch particles and the mixture is compacted or granulated and fired to obtain the objective catalyst excellent in catalyst strength for production of methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen. In the catalyst, the pore volume of pares of <200 nm pore diameter is <0.030 ml/g and the total pore volume in the range of <=20 μm pore diameter is <=30%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation using molecular oxygen to produce methacrylic acid, and to converting methacrolein to molecular oxygen in the presence of this catalyst. The present invention relates to a method for producing methacrylic acid by gas phase catalytic oxidation using methacrylic acid.

[0002]

2. Description of the Related Art The performance of a catalyst used for producing methacrylic acid by gas phase catalytic oxidation of methacrolein using molecular oxygen, particularly the selectivity of methacrylic acid, is greatly affected by the pore structure of the catalyst. That has been known for some time.
For this reason, a catalyst in which the average pore diameter and the pore diameter distribution of the catalyst are controlled, and a method for producing the same have been proposed. For example, in Japanese Patent Publication No. 59-27217, in order to control the average pore diameter of the catalyst, one or more organic substances selected from the group consisting of cellulose, polyvinyl alcohol, polyethylene glycol and gelatin are added and mixed. ,
There is disclosed a method for producing a catalyst having an average pore diameter in a specific range by molding the molded product so that the crushing strength is within a certain range. In the specification, the control of the crushing strength of the molded article closely related to the average pore diameter of the catalyst,
It is described as being particularly important. However, according to the examples, the performance of the obtained catalyst is insufficient for industrial implementation.

[0003] In the specification of Japanese Patent Publication No. Hei 6-79666, M
With respect to a catalyst containing o, P and D (where D is at least one element selected from an alkali metal, an alkaline earth metal and Tl) as an essential component, the distribution range of the pore diameter is as a condition for obtaining high performance. Further, a method for producing a catalyst having such a pore size distribution by granulation using a centrifugal flow coating apparatus is disclosed. However, as can be seen from the examples, satisfactory performance has not been obtained in industrial practice. Further, JP-A-3-86242 and JP-A-4-90853 propose, as catalysts having the same composition, a pore size distribution different from the above as a condition for high performance, and further, as a method for producing the same, A method based on "baking support method" is disclosed. However, the effect of improving the performance is smaller than that of the catalyst produced by the conventional method.

On the other hand, with respect to the catalyst used in the reaction system according to the present invention, there has been proposed a method of improving the performance of a catalyst by adding an organic compound or the like to a catalyst powder or a catalyst raw material powder and performing a heat treatment. Some of them are considered to be expected that the pores finally formed in the catalyst contribute to the improvement of the performance by removing the organic compounds and the like. For example, P, Mo, V and Z (where Z is K, R
With respect to a catalyst containing, as an essential component, at least one element selected from the group consisting of b, Cs, and Tl), a preparation method in which a high molecular weight organic compound is added, molded, and heat-treated is disclosed. However, in the examples, the effect of the addition of the organic compound is small, and satisfactory results have not been obtained. The specification states that this preparation method increases pores over a wide range of about 10 to 1000 nm, and not only pores having a size contributing to performance improvement but also contributing to reduction in catalyst performance. It is conceivable that pores having such a size as to increase are also increased. JP-A-6-374 discloses a preparation method in which activated carbon powder is added to a catalyst component, the mixture is shaped, and heat treatment is performed. However, according to the examples, there is almost no difference in the performance depending on the presence or absence of the addition, and it is hard to say that the effect has appeared. Thus, regarding the catalyst used in the reaction system according to the present invention,
Attempts have been made to improve the production process of catalysts and to improve the performance by additives, but no satisfactory results have been obtained for industrial implementation.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a catalyst which is excellent in the performance of the catalyst, in particular, the methacrylic acid selectivity.

[0006]

Means for Solving the Problems The present inventors have developed a catalyst used for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation using molecular oxygen, in particular, Mo, V, and the like.
Physical properties of a catalyst produced using a catalyst powder containing P, S and Y (where Y is one or more elements selected from the group consisting of K, Rb, Cs and Tl) as essential components,
In particular, as a result of intensive studies on catalysts having excellent performance by controlling the pore structure, a method for producing a catalyst with excellent reproducibility of catalyst performance, improved methacrylic acid selectivity and catalyst strength was found, and the method of the present invention Was completed.

Namely, the present invention has the general formula _{Mo a V b P c S d} X e Y f (NH 4) g O h ( wherein, X is Sb, Si, Cu, Co, the group consisting of Bi and As Y is K,
At least one element selected from the group consisting of Rb, Cs, and Tl; a, b, c, d, e, f, and g represent the atomic ratio of each element; = 0.1 ~
2, c = 1 to 3, d = 0.01 to 1, e = 0.01 to
3, f = 0.1-3, f + g = 2-6, and h is the number of oxygen atoms necessary to satisfy the valence of each component. ), And purified starch particles are mixed, and the mixture is molded or granulated and calcined to reduce the pore volume of pores having a pore diameter of less than 200 nm to 0. Less than 0.030 ml / g and a pore diameter of 20
the total pore volume in the range of μm or less was controlled to 30% or less,
This is a method for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation using molecular oxygen to produce methacrylic acid. Further, the present invention is a method for producing methacrylic acid in which gas phase catalytic oxidation of methacrolein using molecular oxygen in the presence of the catalyst produced by the above production method.

[0008]

In DETAILED DESCRIPTION OF THE INVENTION The present invention of the general formula _{Mo a V b P c S d} X e Y f (NH 4) in _g O _h (wherein, X is Sb, Si, Cu, Co, from Bi and As At least one element selected from the group consisting of
At least one element selected from the group consisting of Rb, Cs, and Tl; a, b, c, d, e, f, and g represent the atomic ratio of each element; = 0.1 ~
2, c = 1 to 3, d = 0.01 to 1, e = 0.01 to
3, f = 0.1-3, f + g = 2-6, and h is the number of oxygen atoms necessary to satisfy the valence of each component. ) And purified starch particles are mixed with each other, and the mixture is molded or granulated and calcined, so that only pores having a size desired for improving the catalyst performance are contained in the catalyst. The methacrylic acid selectivity can be increased with good reproducibility by expressing a large amount of methacrylic acid. When the same preparation is performed without mixing the purified starch particles, it is difficult to express a large number of pores of a desired size with good reproducibility, and it is not always possible to obtain excellent catalytic performance. Further, in the catalyst according to the present invention, since pores having a uniform size are uniformly dispersed in the catalyst, there is no locally low strength portion and a high catalyst strength can be obtained.

[0009] Purified starch particles are generally characterized by a very uniform particle size and a spherical or oval shape. This means that only pores of the desired size for improving catalyst performance are expressed in large amounts in the catalyst, and that pores of uniform size are evenly dispersed, resulting in a catalyst with high performance. Of particular importance for producing good catalysts. With a wide distribution of particle sizes,
When using so-called polydisperse particles instead,
Even pores of an undesirably large size appear, so that the effect of improving the performance is not exhibited, and the catalyst strength is significantly reduced.

The average particle size of the purified starch particles is from 0.2 to
It is preferably in the range of 100 μm. When the average particle size is less than 0.2 μm, 200 nm,
The amount of the following pores increases, and does not give favorable results. Also, as the average particle size increases, the catalyst strength tends to decrease, and when the average particle size is larger than 100 μm, the catalyst strength becomes impractical and should be avoided.

The ratio of the purified starch particles to the catalyst powder is preferably 3 to 40% by weight. If this ratio is less than 3% by weight with respect to the catalyst powder, the amount of pores developed by the addition is small, and the effect of improving the catalyst performance is not sufficiently exhibited. When the ratio exceeds 40% by weight,
Since the amount of the catalyst powder is small, the catalytic activity becomes insufficient for industrial implementation, and at the same time, the catalyst strength is reduced, which is not practical.

[0012] The purified starch particles can be selected from those comprising any starch crystals selected from the group consisting of corn starch, potato, sweet potato, wheat, rice, tapioca, sago and corn. Gives favorable results. These purified starch particles can be easily obtained as commercial products.

The catalyst powder used in the method of the present invention can be prepared by a method usually used in this field, for example, the following method. Molybdenum trioxide, vanadium pentoxide and copper oxide are added to a mixed aqueous solution of sulfuric acid and phosphoric acid,
K, Rb, Cs and Tl are added to the homogeneous solution heated and dissolved under reflux.
A catalyst precursor slurry synthesized by adding a mixed aqueous solution of at least one element selected from the group consisting of, for example, hydroxide and ammonia, at 100 to 250 ° C.
To obtain a catalyst powder.

The mixing of the catalyst powder and the purified starch particles can be easily carried out, for example, by mixing the catalyst powder and the purified starch particles. In addition, the catalyst powder before mixing or the mixed powder of the catalyst powder and the purified starch particles is diluted with an inert substance powder such as silica, alumina, alumina silica, carbon or silicon carbide, or supported on these inert substances. You can also. If necessary, glass fiber, ceramic fiber, carbon fiber, whisker, or the like may be added to the catalyst powder before mixing or the mixed powder of the catalyst powder and the purified starch particles as a strength improving material.

The apparatus and method used for molding or granulating the mixed powder of the catalyst powder and the refined starch particles are not particularly limited, and conventionally known apparatuses and methods can be used. Apparatus and methods generally used for tablet molding, extrusion molding, stirring granulation, bread granulation, tumbling granulation, fluidized granulation and the like can be used. If necessary, silica gel, alumina powder or diatomaceous earth can be used as an auxiliary in molding or granulation. The catalyst produced by molding or granulation is not limited to simply molding or granulating the mixed powder, but may be a supported catalyst in which a molded carrier is coated with the mixed powder. The shape of the catalyst is not particularly limited, and a conventionally known sphere, tablet, ring, spoke ring, convex or convex ring can be used.

[0016] The method and conditions for calcining the catalyst are not particularly limited. It suffices if the purified starch particles are burned off without decomposition or disappearance of the catalytically active component. For example, the reaction can be performed at 150 to 450 ° C. in an air stream for 1 to 48 hours.

The present invention also relates to a method for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation using molecular oxygen in the presence of the catalyst produced by the above-mentioned production method.
The gas-phase catalytic oxidation reaction according to the present invention uses 1 to 1
A mixed gas consisting of 0% by volume of methacrolein, 3 to 20% by volume of molecular oxygen and 70 to 90% by volume of a diluent gas is used, and the gas is placed on the above-mentioned catalyst in a temperature range of 250 to 450 ° C. and normal pressure. Space pressure of 300 to 10 atm
It is performed by introducing at 5000 / hr. Air is usually used as molecular oxygen, but pure oxygen may be used. As a diluting gas, an inert gas such as nitrogen or carbon dioxide is used. Further, a part of the non-condensable gas contained in the reaction gas may be circulated and used. It is preferable to use water vapor as the diluent gas in order to increase the activity and the methacrylic acid selectivity. In that case, the water vapor in the source gas is usually added up to 60% by volume. But,
The present invention can be practiced by using the catalyst of the present invention for the production of methacrylic acid by a method other than the above.

[0018]

The present invention will be described in more detail with reference to examples. The present invention is not limited to the embodiments.
The conversion and methacrylic acid selectivity are defined as follows.

[0019]

## EQU1 ## Conversion (%) = 100 × (moles of reacted methacrolein) / (moles of supplied methacrolein)

[0020]

## EQU2 ## Methacrylic acid selectivity (%) = 100 × (moles of methacrylic acid formed) / (moles of reacted methacrolein)

The catalyst strength is defined by the following drop loss rate and wear rate. 50g of catalyst dropped from a height of 4m
When the weight remaining on the sieve with a mesh size of 2 mm is Ag,

[0022]

## EQU3 ## Falling defect rate (%) = 100 × (50−A) / 50

In addition, 20 g of the catalyst was shaken with a low tap on a sieve having an opening of 1 mm for 60 minutes, and the weight remaining on the sieve was reduced to Bg.
And when

[0024]

## EQU4 ## Abrasion rate (%) = 100 × (20−B) / 20

Example 1 85% phosphoric acid 80.1 was heated and stirred in 6000 ml of water.
g, molybdenum trioxide 1000 g, vanadium pentoxide 6
3 g, 9.7 g of copper oxide and 6.5 g of 95% sulfuric acid were added, and 7
The mixture was heated under reflux for an hour to obtain a homogeneous solution. This is the first raw material
The solution was used. 135% of 28% ammonia water in 420 ml of water
g and 47.3 g of cesium hydroxide and the second raw material solution
did. While maintaining the first raw material solution at 15 ° C. and stirring,
The second raw material solution is dropped, and the obtained slurry is spray-dried.
The composition (atomic ratio) excluding oxygen is Mo₁₂V_1.2P_1.2S
_0.1Cu_0.2Cs_0.5(NH_Four)_3.8Catalyst powder
Was. A purified wheat having an average particle diameter of 2.3 μm was added to this catalyst powder.
10% by weight of starch particles are added to the catalyst powder,
And 8% by weight of ceramic fiber based on catalyst powder
And put it in a 10 liter container and shake for 10 minutes
To obtain a mixed powder. 3mmφ diameter same weight as mixed powder
Flow of spherical alumina silica carrier into rotating drum
While heating the drum wall temperature to 95 to 100 ° C.
Spray the mixed powder obtained above on the body with water while spraying.
Then, the mixture was gradually charged to obtain a supported catalyst. This catalyst is heated at 360 ° C.
For 10 hours in air.

When the pore distribution of this catalyst was measured by a mercury porosimeter, the pore volume of pores having a pore diameter of less than 200 nm was 0.025 ml / g, and the pore volume of pores having a pore diameter of 20 μm or less was determined. The ratio to the total pore volume was 21%. 400 ml of the obtained catalyst was charged into a 1-inch steel reactor, and a raw material gas composition of 3% by volume of methacrolein, 9% by volume of oxygen, 20% by volume of steam, and 68% by volume of nitrogen, a reactor bath temperature of 290 ° C, and a space were used. Speed 800 / h
The reaction was performed under the conditions of r and a reactor outlet pressure of 0.2 kgf / cm ² , and the performance of the catalyst was evaluated. The results are shown in Table 1 together with the catalyst strength.

Example 2 A catalyst was prepared in the same manner as in Example 1, except that purified potato starch particles having an average particle size of 16 μm were used instead of the purified wheat starch particles of Example 1. When the pore distribution of the catalyst was measured with a mercury porosimeter, the pore volume of pores having a pore diameter of less than 200 nm was 0.027 ml / g.
And 22% of the total pore volume. Table 1 shows the strength and performance evaluation results of this catalyst.

Comparative Example 1 To clarify the effect of the purified starch particles on the catalytic performance, a catalyst was prepared in the same manner as in Example 1 except that the purified wheat starch particles were not added. That is, a mixed powder of only a catalyst powder and ceramic fibers was supported on an alumina silica carrier. When the pore distribution of this catalyst was measured with a mercury porosimeter, the pore volume of pores having a pore diameter of less than 200 nm was 0.031 ml / g, which was 52% of the total pore volume. Table 1 shows the physical properties and performance evaluation results of this catalyst.

Comparative Example 2 Instead of the purified wheat starch particles of Example 1, 200
A catalyst was prepared in the same manner as in Example 1 except that meshpass methylcellulose particles were used.
Observation of the methylcellulose fine particles using an electron microscope revealed that the particle size was distributed over a very wide range from 0.2 μm or less to 20 μm or more, and the shape was irregular. When the pore distribution of the prepared catalyst was measured with a mercury porosimeter, it was approximately 10 to 10000 nm.
The pores were irregularly present in the range over the entire measurement region of, and the distribution range of the pores was wide. The pore volume of pores having a pore diameter of less than 200 nm was 0.032 ml / g, which was 26% of the total pore volume. Table 1 shows the physical properties and performance evaluation results of this catalyst.

[0030]

[Table 1] Table 1 強度 Strength Catalyst performance 性能率 Drop loss rate Abrasion rate Conversion rate Methacrylic acid (%) (%) (%) Selectivity (%) ━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 1 0.2 3.4 80.3 88.4 Example 2 1.0 2.3 78.7 86.1 Comparative Example 1 0.7 1.0 75.3 83.9 Comparative Example 2 2.6 26.9 80.3 84.0 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0031]

Industrial Applicability The catalyst produced according to the present invention has excellent catalyst strength and exhibits high methacrylic acid selectivity in the production of methacrylic acid by gas phase catalytic oxidation of methacrolein using molecular oxygen.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tokio Nagayama 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside (72) Inventor Toru Nishimura 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemicals Inc.

Claims (5)

[Claims] 1. A general formula _{Mo a V b P c S d} X e Y f (NH 4) in _g O _h (wherein, X is chosen Sb, Si, Cu, Co, from the group consisting of Bi and As One or more elements, Y is K,
At least one element selected from the group consisting of Rb, Cs, and Tl; a, b, c, d, e, f, and g represent the atomic ratio of each element; = 0.1 ~
2, c = 1 to 3, d = 0.01 to 1, e = 0.01 to
3, f = 0.1-3, f + g = 2-6, and h is the number of oxygen atoms necessary to satisfy the valence of each component. ), And purified starch particles are mixed, and the mixture is molded or granulated and calcined to reduce the pore volume of pores having a pore diameter of less than 200 nm to 0. Less than 0.030 ml / g and a pore diameter of 20
the total pore volume in the range of μm or less was controlled to 30% or less,
A method for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation using molecular oxygen to produce methacrylic acid. 2. The refined starch particles have an average particle size of 0.2 to 0.2.
2. The method according to claim 1, wherein the distance is in the range of 100 [mu] m. 3. The ratio of the purified starch particles to the catalyst powder is 3 to 40% by weight.
Or the method of 2. 4. The purified starch particles are corn starch,
4. It is made of any one of starch crystals selected from the group consisting of potato, sweet potato, wheat, rice, tapioca, sago, and corn.
The method according to any of the above. 5. A method for producing methacrylic acid, comprising subjecting methacrolein to gas-phase catalytic oxidation using molecular oxygen in the presence of the catalyst produced by the method according to claim 1. Description: