JPS584014B2 - Fuhouwa Carbon Sanno Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a corresponding unsaturated carboxylic acid by vapor phase catalytic oxidation of an unsaturated aldehyde using a catalyst of a specific composition. Concerning a suitable method for manufacturing.

Various catalyst systems have been proposed for the production of methacrylic acid by gas phase catalytic oxidation of methacrolein, but these catalysts have advantages and disadvantages.

That is, even if conventional catalysts have low activity or give high yields, they often have shortcomings such as short lifetimes only in the initial stage, and are also important factors in industry. It has drawbacks such as low selectivity and poor reproducibility, and is not necessarily industrially satisfactory.

As a result of intensive research on catalysts used in the above reaction, the present inventors discovered a catalyst containing Mo, P, X, Y and O (where X is selected from the group consisting of V, Fe, pb and Ni). At least one selected metal, Y is K, Rb,
(representing at least one metal selected from the group consisting of Cs and TI), it is possible to obtain the corresponding unsaturated carboxylic acid from the unsaturated aldehyde in extremely high yield and with good reproducibility. It was discovered that the catalyst has a long life and is extremely advantageous for industrial production, and a patent application has already been filed (Japanese Patent Application No. 124910/1982).

The present inventors further researched catalysts suitable for industrialization, and found that Mo, P, K. It has been shown that a catalyst system containing Cs, V and O in specific proportions can produce methacrylic acid with extremely high selectivity, while at the same time suppressing the production of carbon oxides and greatly increasing the yield of methacrylic acid. Heading This invention has been achieved.

The present invention uses the general formula MoaPbKcCsdvoOf (where a, b, c, d, e, and f are the number of atoms of each element) in producing an unsaturated carboxylic acid by gas-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas. Represents the ratio, when a=12, b=0.6 to 1.4, c=
1.0-2.5, d=0.1-1.5, e=01-1.
5, 1.1≦c+d≦3, and f is the number of oxygen sufficient to satisfy the valences of other elements).

The catalyst used in the method of the present invention has very good moldability and excellent physical strength after molding, and can exhibit sufficient performance as a molded catalyst.

Even if an attempt is made to firmly support the catalyst using a binder or the like using a binder or the like, the catalyst supported on the carrier by the usual evaporation to dryness method or the catalyst obtained by classifying the granules of the metal oxide which is the catalyst component using a sieve etc. Even if an attempt is made to improve the physical strength by forming a tablet into a tablet, the performance of the catalyst will generally deteriorate somewhat if the catalyst components are similar.

However, with the catalyst used in the present invention, such a decrease is not observed at all.

Further, when the catalyst of the present invention is used, since the production rate of carbon oxides is low, it also has the feature of excellent temperature controllability of the reactor.

Comparing the catalyst used in the method of the present invention with the catalyst used in the previously patented method, that is, the catalyst containing Mo, P, X, Y, and O, the following can be said. .

That is, the catalyst life can be improved by adding an alkali metal to phosphomolybdic acid, but it has been found that the activity varies greatly depending on the type and amount of the alkali metal added.

For example, addition of lithium or sodium, which are high on the periodic table, greatly reduces activity, which becomes a problem even before life measurement.

The same trend can be seen for potassium, rubidium, and cesium, with the lower the conversion rate in the synchronous rate table, the higher the conversion rate.

However, the selectivity of the reaction decreased slightly, although not as much as the increase in conversion rate, which was an advantage and disadvantage in this reaction where selectivity is important.

Therefore, by creating a mixed system of potassium and cesium, it was discovered that the conversion rate could be increased while maintaining extremely high selectivity in a system with the addition of vanadium, and the influence of each alkali metal on the selectivity and conversion rate. It turns out that is simply not linear.

Therefore, it was found that by varying the ratio of potassium and cesium, the conversion rate and selectivity can be changed appropriately.

In addition, in order to make a highly active catalyst, the amount of alkali metal relative to phosphomolybdic acid is important, and it is related to the sum of the atomic numbers of potassium and cesium. When the atomic ratio of Mo forming phosphomolybdic acid is 12, It is preferable that K+Cs=1.1 to 3.

When K+Cs was outside the above range, an economical decrease in activity was observed in the vanadium-added system.

As a method for preparing the catalyst, conventional methods such as an oxide mixing method and an evaporation to dryness method can be employed.

Catalyst preparation reagents do not necessarily have to be in the form of oxides, but can be metal salts, metal acids or bases, etc., as long as they can be easily oxidized or decomposed and ultimately converted into oxides after catalyst preparation. Either form is acceptable.

Specific examples thereof include nitrates, ammonium salts, and hydroxides.

Catalysts prepared by the above-mentioned methods were heated to 250 -
2-40 at 500°C, particularly preferably 300-450°C
It is preferable to bake for a time.

The catalyst used in the present invention may be molded into tablets, or may be attached to a commercially available molded carrier.

Examples of such carriers include silica, alumina, silicon carbide, pumice, aluminum, sponge, and the like.

As the unsaturated aldehyde, not only methacrolein but also acrolein can of course be used.

According to the present invention, an unsaturated carboxylic acid can be produced in high yield by using a raw material gas containing an unsaturated aldehyde and molecular oxygen mixed with preferably an inert gas and water vapor and passing it over the catalyst of the present invention at high temperature. You can get it.

The reaction conditions are approximately as follows.

(1) Reaction temperature 250-400°C (2) Reaction pressure preferably under normal pressure (3) Space velocity 250-3000 hr-1 (0°C, 1 atm standard) (4) Molar ratio of unsaturated altehyde and oxygen 1:1 -3 (5) Molar ratio of unsaturated aldehyde and water vapor 1:0-50 Air is normally used as the gas containing molecular oxygen, but in addition to pure oxygen, nitrogen, carbon dioxide, helium, argon, and lower saturated It is also possible to use a mixture diluted with a substantially inert gas such as a hydrocarbon.

Analysis in the following examples was by gas chromatography.

Further, the conversion rate, selectivity, and yield were calculated according to the following formula.

In addition, in the following examples, these mol% are simply abbreviated as %.

Example 1 57.0 g (15.6 mmol) of phosphomolybdic acid was placed in a 1 liter beaker to form an aqueous solution.

On the other hand, 4.74 g (46.9 mmol) of potassium nitrate and 1.52 g (7.79 mmol) of cesium nitrate were prepared into an aqueous solution, added to the phosphomolybdic acid aqueous solution, and stirred well.

An aqueous solution of 0.73 g (6.25 mmol) of ammonium metavanadate was further added thereto and stirred well.

This was evaporated to dryness on a hot water bath, transferred to an evaporating dish, and fired at 400° C. for 5 hours in an air atmosphere using a Matsufuru furnace.

Grind the fired product in a mortar and add 5w of graphite powder.
After adding t% and stirring well, it was made into 5mmφ by tablet molding machine.
The pellets were molded into 3 mm x pellets and used as a catalyst.

The atomic ratio in the obtained catalyst components is Mo:P:K:Cs:V
The ratio was approximately 12:1:1.5:0.25:0.2.

25 cc of the above catalyst was packed into a Pyrex glass reaction tube with an inner diameter of 20 mmφ, and the raw material gas with a molar ratio of methacrolein: air: water vapor = 4.6: 35.0: 60.4 was heated at a space velocity of SV = 1000 hr-1. , at a reaction temperature of 340° C., and data were taken 3 to 4 hours after the start of the reaction.

As a result, the conversion rate was -87.7%, and the selectivity to methacrylic acid, acetic acid, and carbon oxides (C0+C02) were 71.5%, 5.3%, and 12.5%, respectively.

Examples 2 and 3, Comparative Examples 1 to 3 Experiments were conducted using the same catalyst preparation method and reaction method as in Example 1, except that the amount of vanadium added was changed.

The results are shown in Table 1. Examples 1 to 3 and Comparative Examples 1 to
From the results of 3, it can be seen that if the amount of vanadium added is selected within a limited range, the selectivity to methacrylic acid is significantly improved.

Examples 4 to 6 Experiments were conducted using the same catalyst preparation method and reaction method as in Example 1, except that the amount of cesium added was changed.

The results are shown in Table 1. Examples 7 and 8 Experiments were conducted using the same catalyst preparation method and reaction method as in Example 1, except that the amount of potassium added was changed.

The results are shown in Table 1. Examples 9 and 10 Experiments were conducted using the same catalyst preparation method and reaction method as in Example 1, except that the amounts of cesium and potassium added were varied.

The results are shown in Table 1. Comparative Examples 4 to 9 When the amount of each element of potassium and/or cesium used is outside the limited range using the same catalyst preparation method and reaction method as in Example 1, and when the total amount of potassium and cesium is outside the limited range An experiment was conducted in the case of

The results are shown in Table 1. Examples 4-10 and Comparative Examples 4-9
It can be seen that if the amount of potassium or cesium added is selected within a limited range, and the total amount of potassium and cesium added is selected within a limited range, a catalyst with significantly superior catalytic activity can be obtained.

Examples 11, 12, Comparative Examples 10, 11 Same as Example 1 except that ammonium paramolybdate aqueous solution or orthophosphoric acid aqueous solution was further added to the phosphomolybdic acid aqueous solution to change the composition ratio of phosphorus to molybdenum. Experiments were conducted using catalyst preparation methods and reaction methods.

The results are shown in Table 1. These results show that if the amount of vanadium added is selected within a limited range, the conversion rate can be significantly improved.

Example 11 The experiment in Example 2 was continued as it was, and the results were obtained 2000 hours after the start of the reaction.

At a conversion rate of 80.1%, selectivity to methacrylic acid, acetic acid, and carbon oxides were 79.5%, 4.8%, and 9.5%, respectively.
The yield of methacrylic acid was 63.7%.

Example 12 66.2 g (53.6 mmol) of ammonium baramolybdate was taken, distilled water was added to make an aqueous solution, and a solution prepared by dissolving 3.62 g of 85% orthophosphoric acid in distilled water was added thereto with stirring.

Add 4.74 g (46 g) of potassium nitrate to the mixed solution in advance.
．． An aqueous solution obtained by dissolving 9 mmol) and 1.52 g (7.79 mmol) of cesium acetate in distilled water was added.

The mixture was evaporated to dryness on a water bath.

The following was calcined, pulverized, and molded in the same manner as in Example 1 to obtain a catalyst.

The atomic ratio of the obtained catalyst was Mo:P:K:Cs:V=1
The ratio was 2:1:1.5:0.25:0.4.

As a result of carrying out the reaction in the same manner as in Example 1, the conversion rate was 78.
At 3%, the selectivities to methacrylic acid, acetic acid, and carbon oxides were 742%, 64%, and 12.5%, respectively, and the yield of methacrylic acid was 58.1%.

Comparative Examples 12 and 13 An experiment was conducted using the same catalyst preparation method and reaction method as in Example 1, except that rubidium or thallium was used instead of cesium.

The results are shown in Table 2. It can be seen that rubidium does not increase the conversion rate as much as cesium, but thallium decreases the selectivity.

Comparative Examples 14 and 15 An experiment was conducted using the same catalyst preparation method and reaction method as in Example 1, except that rubidium or thallium was used instead of potassium.

The results are shown in Table 2. Comparative Example 16 An experiment was conducted using the same catalyst preparation method and reaction method as in Example 1, except that rubidium and thallium were used instead of potassium and cesium.

The results are shown in Table 2.

Comparative Examples 17-19 Except for using iron, lead, and nickel instead of vanadine,
An experiment was conducted using the same catalyst preparation method and reaction method as in Example 1.

The results are shown in Table 2. Comparative Examples 20 to 25 Catalysts having the compositions shown in Table 3 were prepared in the same manner as in Example 1, and the reaction was carried out under the same conditions as in Example 1.

The reaction results are shown in Table 3.

Claims (1)

[Claims] 1. In producing an unsaturated carboxylic acid by gas phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas, the general formula (where a, b, c, d, e and f are Represents the atomic ratio, when a-12, b=0.6 ~ 1.4.c=
1.0-2.5, d=0.1-1.5, e-0.1-1
5. A method for producing an unsaturated carboxylic acid, which comprises using a catalyst represented by the following formula: 1.1≦c+d≦3 and f is the number of oxygen sufficient to satisfy the valences of other elements.