JP2814321B2 - Method for producing methacrylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing methacrylic acid by gas phase catalytic oxidation of methacrolein.

[0002]

2. Description of the Related Art In producing methacrylic acid by gas phase catalytic oxidation of methacrolein, a large number of phosphorus, molybdenum, and vanadium-based multicomponent catalysts are known. It is also known that it is advantageous to keep the yield high at a low reaction temperature from the viewpoint of suppression of side reactions and the cost of the apparatus, but the use of a catalyst prepared by a conventional method does not always give satisfactory results. Not obtained. It is also well known that ammonium paramolybdate or molybdenum trioxide can be used as a molybdenum raw material when preparing the above catalyst. However, the reaction results are not sufficient, the catalyst activity is greatly reduced with time, the reaction temperature is too high, or the reproducibility of the catalyst preparation method is lacking. At present, further improvement is desired.

[0003]

The object of the present invention is to provide a catalyst for a process for advantageously producing methacrylic acid from methacrolein.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a multi-component solid catalyst containing phosphorus, molybdenum, vanadium and copper, comprising a catalyst dry powder prepared by using ammonium paramolybdate as a raw material of a molybdenum component and trioxide. A method for producing methacrylic acid by gas phase catalytic oxidation of methacrolein, comprising using a catalyst obtained by mixing a dry catalyst powder prepared using molybdenum.

[0005] As the methacrylic acid production catalyst obtained by the method of the present invention, the general formula _{P a Mo b V c Cu d} X e Y f Z g O h ( respectively in P, Mo, V, Cu and O wherein phosphorus , Molybdenum, vanadium, copper and oxygen, X is at least one element selected from the group consisting of arsenic, bismuth, antimony, germanium, zirconium, tellurium, silver, silicon and boron, Y is titanium, tungsten, iron, zinc, Chromium, magnesium, tantalum, manganese, barium, gallium, cerium and at least one element selected from the group consisting of lanthanum, Z is at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, a, b, c, d, e, f, g and h indicate the atomic ratio of each element, and when b = 12, a = 0.
1-3, c = 0.01-2, d = 0.01-1, e = 0
, F = 0-3, and g = 0.01-3, and h is the number of oxygen atoms necessary to satisfy the valence of each component.)

In the present invention, a dry powder of a multi-component catalyst containing phosphorus, molybdenum, vanadium and copper is produced using ammonium paramolybdate as a molybdenum raw material, while the same kind of multi-component catalyst using molybdenum trioxide as a molybdenum raw material. A dry powder of the component catalyst is produced, and both are mixed to prepare a molded catalyst.

For the preparation of these two types of catalysts, conventionally known preparation methods may be used. For example, JP-A-2-22243 discloses an example of a catalyst prepared by using ammonium paramolybdate as a raw material for molybdenum. Specifically, a catalyst raw material containing phosphorus, molybdenum and vanadium is dissolved or dispersed in water. The raw material mixture or slurry is evaporated to dryness while heating and stirring. The obtained solid is dried and then crushed to obtain a dried catalyst powder. Further, as a preparation example of a catalyst prepared by using molybdenum trioxide as a raw material of molybdenum, there is Japanese Patent Application No. 2-35855. Prepare a dry catalyst powder in the same manner. As a raw material compound of a catalyst constituent element other than molybdenum, oxides, carbonates, nitrates, acetates, hydroxides and the like can be used in combination. The two types of catalyst compositions are preferably the same, but may be different.

As a method for mixing the two kinds of dry powders thus obtained, mixing in a dry state, that is, dry mixing may be used, or an appropriate amount of water may be added to form a slurry, and the slurry may be mixed. Mixing, that is, wet mixing may be used. The mixing ratio of the dry powder prepared from ammonium paramolybdate and the dry powder prepared from molybdenum trioxide was 0.05: 0.95 to 0.95: 0.0 by weight.
5, but it is particularly preferable to select from 0.1 to 0.9 to 0.9 to 0.1. The dried mixed powder thus obtained is molded and heat-treated under a flow of air to obtain a target catalyst.

Although the catalyst obtained by the method of the present invention is effective without a carrier, it is supported on an inert carrier such as silica, alumina, magnesia, titania, silica / alumina, silicon carbide, or mixed and diluted with the same. It can also be used.

In practicing the present invention, the concentration of methacrolein in the raw material gas is not particularly limited, but usually 1 to 20% by volume is appropriate, and particularly preferably 3 to 10% by volume. The raw material methacrolein may contain small amounts of impurities such as water and lower saturated aldehyde, and these impurities do not substantially adversely affect the reaction.

Although it is economical to use air as the oxygen source, air enriched with pure oxygen may be used if necessary.
The oxygen concentration in the source gas is defined by the molar ratio to methacrolein, and this value is 0.3 to 4, especially 0.4 to 2.5.
Is preferred. The source gas may be diluted by adding an inert gas such as nitrogen, steam, or carbon dioxide. The reaction pressure is preferably from normal pressure to several atmospheres. The reaction temperature can be selected in the range of 230 to 450 ° C, and particularly preferably 250 to 400 ° C. The reaction can be carried out in a fixed bed or a fluidized bed.

[0012]

EXAMPLES Hereinafter, a method for preparing a catalyst according to the present invention, and
A reaction example using the same will be specifically described. In Examples and Comparative Examples, the reaction rate of methacrolein and the selectivity of methacrylic acid to be formed are defined as follows.

[0013]

(Equation 1)

Parts in the following Examples and Comparative Examples are parts by weight, and the analysis was carried out by gas chromatography.

Example 1 100 parts of ammonium paramolybdate, 2.8 parts of ammonium metavanadate and 9.2 parts of cesium nitrate were dissolved in 100 parts of pure water. To this was added a solution of 8.7 parts of 85% phosphoric acid dissolved in 30 parts of pure water. Next, copper nitrate 1.
A solution obtained by dissolving 1 part in 30 parts of pure water was added. The obtained mixed liquid is referred to as Liquid A. On the other hand, 100 parts of molybdenum trioxide,
2.6 parts of vanadium pentoxide and 10.7 parts of 85% phosphoric acid were added to 400 parts of pure water and heated under reflux for 3 hours. To this was added 0.5 parts of copper oxide, and the mixture was further heated and refluxed for 2 hours. After refluxing, 11.2 parts of cesium bicarbonate dissolved in 100 parts of pure water were added, and then ammonium carbonate 5 dissolved in 50 parts of pure water was added.
Parts were added. The obtained mixed liquid is referred to as Liquid B. Liquid A and B
The liquids were evaporated to dryness while separately heating and stirring. The obtained solid was dried at 120 ° C. for 16 hours and then pulverized.

Next, the powder obtained from the liquid A and the powder obtained from the liquid B are mixed at a weight ratio of 1: 1 and then molded under pressure and heat-treated at 380 ° C. for 3 hours under air flow. Used as catalyst. The composition of the resulting of elements other than oxygen in the catalyst (the same applies hereinafter) was _{P 1.6 Mo 12 V 0.5 Cu 0.1} Cs 1. This catalyst was charged into a reactor and methacrolein 5
%, Oxygen 10%, steam 30% and nitrogen 55% (vol%) at a reaction temperature of 290 ° C. for a contact time of 3.6 seconds. The product was collected and analyzed by gas chromatography. As a result, the conversion of methacrolein was 86.0% and the selectivity of methacrylic acid was 84.4%.

Comparative Example 1 A catalyst was prepared in the same manner as in Example 1 except that only the powder obtained from the solution A of Example 1 was pressed and molded. The composition of the elements of this catalyst is the same as in Example 1. When the reaction was carried out using this catalyst under the same conditions as in Example 1, the conversion of methacrolein was 82.0% and the selectivity of methacrylic acid was 8%.
2.1%.

Comparative Example 2 A catalyst was prepared in the same manner as in Example 1 except that only the powder obtained from the solution B of Example 1 was used for pressure molding. When a reaction was carried out using this catalyst under the same conditions as in Example 1, the conversion of methacrolein was 86.1% and the selectivity of methacrylic acid was 82.5%.

Example 2 100 parts of ammonium paramolybdate, 3.9 parts of ammonium metavanadate, 1.4 parts of potassium nitrate and 4.9 parts of rubidium nitrate were dissolved in 100 parts of pure water. A solution of 7.6 parts of 85% phosphoric acid, 1.1 parts of copper nitrate, and 3.8 parts of ferric nitrate in 30 parts of pure water was sequentially added thereto. Subsequently, 1.5 parts of germanium oxide and 0.6 part of boric acid were added. The obtained mixed liquid is referred to as Liquid A.

On the other hand, 100 parts of molybdenum trioxide, 4.7 parts of ammonium metavanadate, and 9.3 of 85% phosphoric acid are used.
, 1.8 parts of germanium oxide and 0.7 part of boric acid were added to 400 parts of pure water, and the mixture was refluxed for 3 hours. A solution prepared by dissolving 1.4 parts of copper nitrate and 4.7 parts of ferric nitrate in 30 parts of pure water was added thereto, and the mixture was further heated under reflux for 2 hours. After the reflux, 1.8 parts of potassium nitrate dissolved in 30 parts of pure water and 6.0 parts of rubidium nitrate dissolved in 50 parts of pure water were added, followed by 10 parts of ammonium nitrate dissolved in 100 parts of pure water. The obtained mixed liquid is referred to as Liquid B. The solution A and the solution B were evaporated to dryness while separately heating and stirring. The obtained solid was dried at 120 ° C. for 16 hours and then pulverized.

Next, 100 parts of the powder obtained from the solution A and B
30 parts of pure water was added to 100 parts of the powder obtained from the liquid to form a slurry and mixed. The obtained mixed slurry was dried again at 120 ° C. for 16 hours, and then pulverized. This powder was molded under pressure, and heat-treated at 380 ° C. for 3 hours in an air stream to use as a catalyst. The composition of the resulting elements of the _{catalyst, P 1.4 Mo 12 V 0.7 Cu} 0.1 Fe 0.2 Ge 0.3 B 0.2 K
_0.3 Rb _0.7 . When a reaction was carried out using this catalyst under the same conditions as in Example 1, the conversion of methacrolein was 90.5% and the selectivity of methacrylic acid was 89.6%.

Comparative Example 3 A catalyst was prepared in the same manner as in Example 2 except that pressure molding was performed using only the powder obtained from the solution A in Example 2. When a reaction was carried out using this catalyst under the same conditions as in Example 1, the conversion of methacrolein was 88.0% and the selectivity of methacrylic acid was 86.5%.

Comparative Example 4 A catalyst was prepared in the same manner as in Example 2, except that only the powder obtained from the solution B of Example 2 was used for pressure molding. When the reaction was carried out using this catalyst under the same conditions as in Example 1, the conversion of methacrolein was 90.6% and the selectivity of methacrylic acid was 87.7%.

Examples 3-8 Weight of dry powder obtained from liquid A (using ammonium paramolybdate as a raw material for molybdenum component) and dry powder obtained from liquid B (using molybdenum trioxide as a raw material for molybdenum component) Except for changing the mixing ratio, each catalyst of Table 1 was prepared according to Example 1. The reaction was carried out under the same conditions as in Example 1 except for the reaction temperature, and the results shown in Table 1 were obtained.

Comparative Examples 5 to 10 Each of the comparative catalysts in Table 1 was prepared using only the powders obtained from the solutions A of Examples 3 to 8, respectively. The reaction was carried out under the same conditions as in Example 1 except for the reaction temperature, and the results shown in Table 1 were obtained.

Comparative Examples 11 to 16 Each comparative catalyst shown in Table 1 was prepared using only the powders obtained from the solutions B of Examples 3 to 8. The reaction was carried out under the same conditions as in Example 1 except for the reaction temperature, and the results shown in Table 1 were obtained.

[0027]

[Table 1]

[0028]

The catalyst used in the method of the present invention has an effect of improving the performance as compared with the case where ammonium paramolybdate is used as a raw material of the molybdenum component and the case where molybdenum trioxide is used.

Claims (2)

(57) [Claims] 1. A catalyst drying powder prepared by using ammonium paramolybdate as a raw material of a molybdenum component and a catalyst drying powder prepared by using molybdenum trioxide in a multi-component catalyst containing phosphorus, molybdenum, vanadium and copper. A method for producing methacrylic acid by gas phase catalytic oxidation of methacrolein, comprising using a catalyst obtained by mixing powder and powder. 2. A catalyst for producing methacrylic acid has the general formula _{P a Mo b V c Cu d} X e Y f Z g O h ( respectively in P, Mo, V, Cu and O wherein phosphorus, molybdenum, vanadium, Copper and oxygen, X is at least one element selected from the group consisting of arsenic, bismuth, antimony, germanium, zirconium, tellurium, silver, silicon and boron, Y is titanium, tungsten, iron, zinc, chromium, magnesium, tantalum , At least one element selected from the group consisting of manganese, barium, gallium, cerium and lanthanum, Z is at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, a, b, c, d , E, f, g and h indicate the atomic ratio of each element, and when b = 12, a = 0.
1-3, c = 0.01-2, d = 0.01-1, e = 0
-3, f = 0-3, g = 0.01-3, and h is the number of oxygen atoms necessary to satisfy the valency of each component described above.) The method according to claim 1, characterized in that: