JPH0631172A - Catalyst for production of methacrylic acid - Google Patents

Abstract

PURPOSE:To provide a catalyst for production of methacrylic acid having high practicality as well as high activity, high selectivity and a long service life. CONSTITUTION:A spherical inert carrier having 2-10mm diameter is coated with powder of a catalytically active material having 10-20m<2>/g specific surface area. The catalytically active material is represented by PaMobVcCedCueYfOg [where P, Mo, V, Ce, Cu and O are phosphorus, molybdenum, vanadium, cerium, copper and oxygen, respectively, Y is at least one among potassium, rubidium, cesium and thallium, (a)-(g) show the atomic ratio among the elements, and when (b) is 12, (a) is 0.5-3, (c) is 0.1-3, (d) is 0-3, (e) is 0-3, (f) is 0.01-2 and (g) is the number of oxygen atoms required to satisfy the valences of the elements]. The objective catalyst for production of methacrylic acid is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein.

[0002]

2. Description of the Related Art Conventionally, many patents have been proposed regarding a method for producing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde. These are mainly a method for producing acrylic acid from acrolein, and claims have been made to include the production of methacrylic acid from methacrolein, but an example of an oxidation reaction of methacrolein is specifically disclosed. Those that are rare are rare.
Further, even if it is disclosed, when the oxidation reaction of methacrolein is actually carried out by these catalysts, the combustion reaction of methacrolein is remarkable in many cases, and the change rate, the selectivity and the production amount are often extremely low, and It had a short life and was not practical.

On the other hand, many catalysts have been proposed in recent years for the method of producing methacrylic acid from methacrolein. For example, JP-A-50-41811 and JP-A-53-
There are 3165 etc.

However, the reaction results and the catalyst life are still insufficient, and they are unsatisfactory for industrially producing methacrylic acid.
The reason for the poor reaction results is that the reaction for producing methacrylic acid is an exothermic reaction with a significantly large amount of heat generation, and the heat storage in the catalytically active substance is large. In particular, there is a drawback that not only the excessive oxidation reaction at a locally abnormally high temperature called a hot spot progresses and the yield is lowered, but also the life of the catalyst is shortened by a heat load. There is Kaihei 3-86242. According to this patent, a method of supporting a slurry of the catalyst on an inert carrier is proposed as a method for improving these drawbacks. However, in the case of this method, since a part of the dissolved catalytically active component penetrates into the inside of the pores of the carrier because the catalyst slurry is used, an excessive oxidation reaction proceeds, leading to a decrease in yield.

Thus, in the case of the prior art, the reaction results,
At present, there is a defect in the catalyst life, and further improvement is desired when used as an industrial catalyst.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides an industrially advantageous method for producing methacrylic acid from methacrolein.
For the purpose of developing a catalyst having high activity and a long catalyst life, as a result of extensive studies, by coating a catalyst active component powder mainly composed of molybtovanaline acid, which is well known in the past, on an inert carrier, the activity, It has been found that the catalyst becomes highly practical as well as selectivity and life, and a method for producing methacrylic acid using this catalyst is provided.

[0007]

[Means for Solving the Problems] That is, the present invention relates to methacrylic acid comprising a catalyst in which a powder of a catalytically active substance having a specific surface area of 10 to 20 m ² / g is coated on an inert carrier having a spherical shape of ² to 10 μm. a catalyst for producing the catalyst active substance, the right formula _{P a Mo b V c Ce d} Cu e
Y _f O _g (where P, Mo, V, Ce, Cu, and O represent phosphorus, molybdenum, vanadium, cerium, copper, and oxygen, and Y is selected from potassium, rubidium, cesium, and / or thallium. Indicates at least one, a,
b, c, d, e, f, b, h represent atomic ratios of the respective elements, and when b = 12, a = 0.5 to 3, c = 0.1 to
3, d = 0 to 3, e = 0 to 3, f = 0.01 to 2, and g represent the number of oxygen atoms required to satisfy the valence of each component. ) Is a catalyst for methacrylic acid production.

Since the catalyst of the present invention has a high activity and a high selectivity, there is no abnormal heat generation in the catalyst layer due to complete combustion, and as a result, a high catalyst activity is maintained for a long period of time, which is of great industrial value. large.

The present invention will be described in detail below.

The methacrylic acid-producing catalyst of the present invention comprises an inert carrier and a catalytically active substance supported on the carrier.
As the inert carrier, known ones generally used such as silicon carbide, silica, α-alumina, silica-alumina, titania and other refractories can be used. Regarding the shape of the inert carrier, it is necessary to have a spherical shape of 2 to 10 μm. In the case of pellets, rings, or the like, it is difficult to uniformly support the catalytically active powder on the carrier, and it is difficult to sufficiently exert the effects of the present invention. . In order to coat the catalytically active powder firmly on the carrier, it is preferable that the carrier has a rough outer surface.

The catalytically active substances represented by the above formula are P, M
A compound containing o, V, Ce, Cu, Y and O is mixed, further heated if necessary, and dried to obtain a catalytically active powder.

As another important requirement of the present invention, it is necessary to control the specific surface area of the catalytically active powder to 10 to 20 m ² / g.

The specific surface area of the catalytically active component layer in the present invention is measured by a fully automatic surface area measuring device (Okura Riken Co., Ltd.). If the specific surface area is less than 10 m ² / g, the catalytic activity will be too low, while if it exceeds 20 m ² / g, the selectivity of methacrylic acid will decrease, which is not preferable. Examples of methods for controlling the specific surface area to 10 to 20 m ² / g include the following methods.

An aqueous solution of ammonium paramolybdate,
The desired product can be obtained by mixing an aqueous solution of metavanadic acid and a catalyst component such as phosphoric acid and then spray-drying. When the slurry obtained by heating and concentrating the catalyst component-containing aqueous solution by a usual method is dried, the specific surface area is generally 10 m ² /
It is less than g, which is not preferable. However, the method for controlling the surface area within this range is not restricted in any way, and any method manufactured by a method with a specific surface area of 10 to 20 m ² / g can be applied. In the present invention, as a method for coating the catalytically active substance on the inert carrier, it can be supported by a general method such as a Marumerizer method or a centrifugal fluidized coating method. Usually, the amount of the catalytically active substance loaded on the inert carrier is preferably 20 to 300 g per 100 ml of the carrier. When it is less than 20 g, the amount of the catalytically active substance is too small and the activity is lowered, while when it is more than 300 g, the layer of the catalytically active substance becomes thick and it is difficult to achieve the object of the present invention.

Water is generally used as a binder liquid that plays a role of firmly adhering to a carrier, but organic substances such as polyvinyl alcohol, carboxymethylserose, and hydroxymethylserose are used for the purpose of adhering it more strongly. It is also possible to spray an aqueous solution of the above or an aqueous solution of silica sol. The use of an aqueous solution of silica sol is particularly preferred. The amount of the binder used may be such that spraying is not impaired.

When the present invention is carried out, the particle size of the catalyst powder has a great influence on the adhesion to the carrier, and the particle size of 95% or more is 1%.
It is important that the thickness is 000 μm or less. Furthermore, 500
It is preferable that 80% or more of particles having a particle diameter of μm or less are contained. If the particle size is 1000 μm or more, the adhesion of the carrier becomes weak, and when used as a catalyst, the catalyst may be desorbed, which makes it difficult to use.

When using the catalyst for producing methacrylic acid of the present invention to produce methacrylic acid by gas phase oxidation of methacrolein, isobutyraldehyde or isobutyric acid, or a mixture thereof, the apparatus and conditions for carrying out the method are particularly There is no limit.

For example, for 1 to 10% by volume of methacrolein, isobutyraldehyde or isobutyric acid, molecular oxygen in a range of 1 to 5 times by volume and an inert gas such as water vapor or nitrogen is used as a diluent. , Reacts in the presence of carbon dioxide. The use of water vapor as the inert gas suppresses side reactions and is advantageous for improving the selectivity to the target substance.

The reaction may be carried out under normal pressure, increased pressure or reduced pressure, but it is generally convenient to carry out under normal pressure. The reaction temperature is 230 to 400 ° C, preferably 250
A temperature of ~ 360 ° C is suitable. The contact time varies depending on the reaction time, but is 0.1 to 15 seconds, preferably 0.5 to 10 seconds.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof.

In Examples and Comparative Examples, the rate of change of methacrolein and the selectivity of methacrylic acid produced are defined as follows.

[0022]

[Formula 1]

[0023]

[Formula 2]

[0024]

EFFECT OF THE INVENTION The catalyst for producing methacrylic acid of the present invention is excellent in thermal stability and gives a target compound with a high rate of change and selectivity.

[0025]

Example 1 To 3 liters of ion-exchanged water, 1000 g of ammonium paramolybdate was added and heated to 75 ° C. to dissolve. Add ammonium metavanadate 28 to this solution.
g was added and dissolved. 250m of this ion-exchanged water
138 g of cerium nitrate was added to 1 and the solution which was heated to 75 ° C. and dissolved was added. Further, 160 g of an aqueous solution containing 65.3 g of 85% phosphoric acid and heated to 75 ° C. was added to the solution.

On the other hand, 1 ml of copper nitrate was added to 300 ml of deionized water.
1.4 g was dissolved by heating, and 8.1 g of participating cerium was further added to prepare a suspension, which was added to the aqueous solution and stirred under heating to obtain a slurry.

This slurry was centrifugally rotated at a rotation speed of 2 using SD-12.5 type manufactured by Ashizawa Atomizer Co., Ltd.
0000r. p. m, a drying inlet temperature of 280 ° C., an outlet temperature of 140 ° C., and a slurry supply rate of 6.5 liters / hour were spray-dried to obtain a catalyst powder. The particle size distribution of the catalyst powder is 10% below 31 μm, 50% below 70 μm,
90% was 154 μm or less and 100% was 350 μm or less. This catalyst powder was used as a fluffy plate as a fluffy plate using a Malmizer Q230 type manufactured by Fuji Paudal Co., Ltd.
Using a combination of knurls and a carrier of 3.5 mmΦ α-A
l ₂ O ₃ (Shikishima Marubi Co., Ltd. Ma-2063.5)
While spraying 1000 g of the catalyst powder on 1000 ml, water was simultaneously sprayed for coating. The obtained coated catalyst was calcined at 350 ° C. for 30 hours in an air stream to obtain a catalyst.

The composition of the active material layer of this catalyst (excluding oxygen) is Mo ₁₂ , P _1.2 , V _0.5 , Cu _0.1 , C in atomic ratio.
e _0.1 , CS _1.5 , the specific surface area of the catalytically active substance is 15 m ²
/ G.

This catalyst was charged into a reactor, and a mixed gas consisting of 5 mol% of methacrolein, 10 mol% of oxygen, 30 mol% of steam and 55 mol% of nitrogen was supplied at a space velocity of 1000 hr ^-1.
The reaction was carried out at a reaction bath temperature of 285 ° C. The maximum temperature of the catalyst layer was 311 ° C, and the methacrolein conversion rate was 83.1.
A selectivity of methacrylic acid of 85.3% was obtained. After the reaction was continued for 1230 hours under the same conditions, the activity value was 83.6% for methacrolein and 84.
No decrease in activity was observed at 9%.

[0030]

Comparative Example 1 A catalyst having the same composition as in Example 1 was used in Example 1.
A catalyst slurry was obtained in the same manner as in. The catalyst slurry was heated and concentrated, dried at 120 ° C., pulverized, coated on a carrier in the same manner as in Example 1, and calcined to obtain a catalyst. The specific surface area of the catalytically active substance was 7 m ² / g. The reaction was carried out under the same conditions as in Example 1 except that the reaction bath temperature was changed to 330 and 350 ° C.

As a result, when the reaction bath temperature was 330, the methacrolein conversion rate was 30.4% and the methacrylic acid selectivity was 9%.
Yielded 1.3%. At a reaction bath temperature of 350, the methacrolein conversion rate was 73.4% and the methacrylic acid selectivity was 40.
Obtained 5%.

[0032]

Comparative Example 2 The spray-dried catalyst powder obtained in Example 1 has a diameter of 5 m.
The catalyst was obtained by molding into a cylinder having a diameter of m and a length of 2.5 mm and firing under the same conditions as in Example 1.

As a result of reacting under the same conditions as in Example 1,
The temperature of the catalyst layer rose to 407 ° C., and stable results could not be obtained.

[0034]

Example 2 The catalyst powder obtained in Example 1 was added to 1000 ml of 3.5-mmΦ α-Al ₂ O ₃ (Ma-2063.5 manufactured by Shikishima Marubi Co., Ltd.) in the same manner as in Example 1. While spraying 2000 g, 5% silica sol was simultaneously sprayed for coating. The obtained coated catalyst was placed under an air stream of 35
The catalyst was obtained by calcining at 0 ° C. for 30 hours.

The coated catalyst was vigorously shaken on a 16 mesh screen for 152 minutes (low tap standard sieve shaker SS
-100, used by Marubishi Scientific Machinery Co., Ltd.) The wear strength was measured and found to be 0.3%.

[0036]

[Formula 3] In addition, as a result of conducting a strength test for 100 particles by dropping the coated catalyst onto the iron plate from above 3 m, no coating peeling or cracking was observed at all.

As a result of measuring the catalytic activity under the same reaction conditions as in Example 1, the conversion of methacrolein was 82.8% and the selectivity of methacrylic acid was 85.7%.

[0038]

Examples 3 to 5 Catalysts having various compositions were prepared according to Example 1, and the activity was evaluated under the same reaction conditions as in Example 1. The results are shown in Table 1.

[0039]

Comparative Examples 3 to 5 Catalysts having various compositions were prepared according to Example 1, and the activity was evaluated under the same reaction conditions as in Example 1. The results are shown in Table 1.

[0040]

[Table 1]

Claims (3)

[Claims] 1. A catalyst for methacrylic acid production, comprising a catalyst in which a powder of a catalytically active substance having a specific surface area of 10 to 20 m ² / g is coated on an inert carrier having a spherical shape of ² to 10 mm. The substance is the formula on the right, P _a Mo _b V _c
Ce _d Cu _e Y _f O _g (where P, Mo, V, Ce, C
u and O represent phosphorus, molybdenum, vanadium, cerium, copper and oxygen, Y represents at least one selected from potassium, rubidium, cesium, and / or thallium, and a, b, c, d, e, f and g represent the atomic ratio of each element, and when b = 12, a = 0.5 to 3, c = 0.1.
-3, d = 0-3, e = 0-3, f = 0.01-2, g
Represents the number of oxygen atoms required to satisfy the valence of each component. ) Is a catalyst for producing methacrylic acid. 2. The catalyst for producing methacrylic acid according to claim 1, which is composed of powder of a catalytically active substance having a particle size of 1000 μm or less and 95% or more. 3. The catalyst for producing methacrylic acid according to claim 1, which is made of powder of a catalytically active substance having a particle size of 500 μm or less and 80% or more.