JPS6023670B2 - Manufacturing method of methacrylonitrile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing methacrylonitrile by gas phase catalytic reaction of isobutene, molecular oxygen and ammonia.

More specifically, the present invention relates to a method for producing methacrylonitrile by reacting isobutene, molecular oxygen, and ammonia in the gas phase in the presence of a molybdenum-bismuth-antimony catalyst with improved catalytic performance. Various proposals have been made regarding the method of producing unsaturated nitriles by the reaction of olefins with molecular oxygen and ammonia, that is, by the ammoxidation reaction of olefins. However, most of them are related to the ammoxidation reaction of propylene, and relatively few are related to the ammoxidation reaction of isobutene. In many cases, the ammoxidation reaction of isobutene is simply tested using a propylene ammoxidation catalyst, and the isomoxidation reaction of propylene and isobutene is treated as the same. However, propylene and isoptene have significantly different reactivities, and the reaction rate of the latter is considerably higher than that of the former. In addition, the selectivity of the desired product usually differs considerably for the same catalyst. Therefore, catalysts used in the industrial production of methacrylonitrile through ammoxidation reactions must be researched and developed as such. The works considered from this point of view are:
Catalysts mainly composed of molybdenum, bismuth, and antimony described in Japanese Patent Publication No. 39-10111 and improved catalysts described in Japanese Patent Publication No. 39-26391 and Japanese Patent Publication No. 48-15283, and various other catalysts. Mochiko No. 47-3327, No. 39025, No. 101331, Tokko No. 49-117425, No. 665 No. 51-665, Tokuko No. 117425, No. 51-665, and Examples include the catalyst described in Japanese Patent Publication No. 53-137915. However, these catalysts still have many problems from the viewpoint of industrial use. For example, insufficient yield of the desired product;
These include a large number of by-products, an inappropriate reaction rate, and the use of elements that are unfavorable from safety and environmental considerations or particularly expensive elements as catalyst components. In recent years, ammoxidation catalysts for the production of unsaturated nitriles include:
There are many proposals for multi-component molybdenum catalysts, most of which contain iron or chromium as essential components in molybdenum/bismuth.

Most of these proposals target the ammoxidation reaction of propylene, and although the ammoxidation reaction of isobutene is mentioned, this is merely a reference example. Compared to propylene, isobutene has a significantly higher reaction rate, and the addition of iron or chromium to the molybdenum-bismuth catalyst has a negative effect on the selectivity of methacrylonitrile, and the reaction rate is also excessive, making it unsuitable as a practical catalyst. It is very useful to use. There are also some that mention the addition of alkali metals, and others that mention the addition of thallium, which has similar behavior.

However, these are not suitable for use in the ammoxidation reaction of isobutene because the amount added is small and the reaction rate is highly dependent on temperature. Furthermore, the use of m, which is highly toxic, is not preferred for industrial use. Therefore, the present inventors conducted research with the aim of developing a catalyst to advantageously advance the methacrylonitrile production reaction by ammoxidation of isobutene.
Mo-B described in Japanese Patent Publication No. 38-23611, Japanese Patent Publication No. 39-10111, and Japanese Patent Publication No. 48-15283
By improving the i-Sb-based catalyst, it was possible to make it even more excellent as a practical catalyst.

The main improvement is that by adding a relatively large amount of alkali metals such as sodium, potassium, rubidium, or cesium to molybdenum, bismuth, and antimony, it is possible to obtain a higher methacrylonitrile yield and to reduce the reaction rate. Temperature dependence can be reduced and operability improved (however, among alkali metals, potassium, rubidium, and cesium have a greater effect than sodium), and the addition of nickel improves methacrylonitrile. The selectivity can be improved, a suitable reaction rate can be achieved, and changes in catalyst activity over time can be reduced. The present invention has been achieved based on these findings. That is, the method for producing methacrylonitrile according to the present invention involves converting isobutene, oxygen, and ammonia into the following empirical formula: Mo,2 BiaSbb
NjC Pd Ae ○r (here, A is Na, K,
At least one element selected from the group consisting of Rb and Cs, and the subscripts a, b, c, d, e, and f are Mo
The atomic ratio of each element is shown when it is 2, and a=3
~15 b=2-15, c=1-10, d=0-5, e
This method is characterized in that the reaction is carried out in the presence of a catalyst having a value of 0.3 to 5, f = the number corresponding to the oxide produced by the combination of the above components.

In the catalyst of the present invention, at least one alkali metal component selected from the group consisting of sodium, potassium, rubidium and cesium has an atomic ratio of 12 molybdenum components.
It is suitable to add it at a ratio of 0.3 to 5.
When the alkali metal component is not added or when the amount added is small, the temperature dependence of the reaction rate becomes large, especially on the low reaction temperature side, and when the amount added is large, the methacrylonitrile yield decreases and the reaction rate also decreases. This is not desirable because it becomes smaller. The nickel component is preferably added in an atomic ratio of 1 to 10 to 12 molybdenum components.

If the amount is less than the lower limit, the improvement in methacrylonitrile selectivity will be small, and if the amount is more than the upper limit, the catalyst will have a strong complete oxidation property and the yield of methacrylonitrile will decrease, which is not preferable. The phosphorus component is preferably added in an atomic ratio of 5 or less to 12 molybdenum components.

If the amount added is more than 5, it is not preferable because the catalyst is very likely to crystallize, the reaction rate decreases by 4.0, and the yield of methacrylonitrile also decreases. The atomic ratio of molybdenum, bismuth, and antimony is determined in the range of 12 molybdenum to 3 to 1 bismuth and 2 to 15 antimony.

This is an experimentally determined range in which the effect of adding the alkali metal component, nickel component, and phosphorus component is maximized and a high methacrylonitrile yield can be obtained. The catalyst of the present invention can be produced by any known method.

As the raw material for the antimony component, antimony trioxide, antimony tetroxide, antimony pentoxide, nitrate oxide of antimony metal, mineral acid of antimony, organic acid salt, etc. can be used.

As a raw material for the molybdenum component, molybdenum trioxide, molybdic acid, ammonium molybdate, etc. can be used.

As a raw material for the bismuth component, bismuth trioxide, bismuth nitrate, nitric oxide of metal bismuth, etc. can be used.

Phosphoric acid is preferably used as a raw material for the phosphorus component.

As sources for the sodium, potassium, rubidium, and cesium components, oxides, hydroxides, nitrates, and the like of each component can be used. As the raw material for the nickel component, nickel oxides, hydroxides, nitrate oxides of metallic nickel, and the like can be used.

The catalyst of the present invention can be produced by mixing these catalyst raw materials to a predetermined composition ratio, drying, and firing.

Here, the calcination conditions are important for imparting a predetermined activity to the catalyst.

The catalyst is heated at a temperature of 400°C to 90,000°C in the presence of oxygen. Preferably, the mixture is heated for 1 hour to 5 hours. Although the catalyst of the present invention can be used without a carrier, it is generally advantageous to include silica, alumina, titania, etc. as a carrier in an amount of 10 to 9% by weight based on the total catalyst weight.

The catalyst may be shaped into pellets and used in fixed bed reactions, or it may be shaped into fine particles and used in fluidized bed reactions.

The reaction of the present invention is carried out by sending a mixed gas of isobutene, oxygen, and ammonia to the catalyst layer.

Air is preferably used as the oxygen source. Nitrogen, carbon dioxide, steam, saturated hydrocarbon, etc. can be used as a diluting gas if necessary. The gas supplied to the reactor is
The molar ratio of oxygen/isobutene is preferably 1-5, particularly 2-4, and the molar ratio of ammonia-isobutene is preferably 1-5, particularly 1-2. The oxygen to be supplied may be divided as described in Hakama Kosho No. 23611 and the like.

In some cases, this may increase the yield of the desired product. Some of the catalysts of the present invention have relatively high ammonia combustibility.

In such cases, the combustion of ammonia can be suppressed by adding water vapor. The amount of water vapor to be added is preferably in the range of 0.2 to 3 moles per mole of isobutene. Even if a large amount of steam is used in excess of this range, the reaction content will not be improved and it will be economically disadvantageous.
Using a catalyst with relatively high ammonia combustibility, and
If you do not want to add water, use the method described in Japanese Patent Publication No. 45-4136 to avoid useless combustion of ammonia by introducing some or all of the ammonia downstream from the isobutene supply port. You can also.

If necessary, nitrogen, carbon dioxide, saturated hydrocarbon, etc. can also be added as a diluting gas. The reaction temperature was 300
None, 500pm, especially 380, 480q
o is preferred.

The reaction pressure may be either increased or reduced pressure, but it is practical to carry out the reaction at normal pressure or slightly increased pressure. The contact time is 0.5 to 20 seconds under the reaction conditions.

It may be selected appropriately depending on the activity of the catalyst. The reaction can be carried out in a fixed bed or in a fluidized bed. The present invention will be specifically explained by the following examples.

Example 1 The experimental formula is Mo, 2 Bi6 S wide Ni6 P, K, . oN
father. Illusion 066. , (Sj02)7.

A fixed bed catalyst was prepared as follows. Silica sol (Si02 2 wt%, Na200.04 wt%
) 715.4 grams and 3.9 grams of phosphoric acid (content 85% by weight) were added.

(1) 72.0 g of ammonium paramolybdate was dissolved in 300 g of pure water, and (1) was added.

(b) 59.3 ml of nickel nitrate was added to (0) and mixed. (m) 3.5 hours of potassium nitrate was added to (m).

(W) 5 parts of nitric acid (6% by weight) and 20 parts of pure water were mixed, and 99.0 parts of bismuth nitrate was added and dissolved. This (W
) was added. (V) Finally, 29.8 g of antimony trioxide was added.

This was heated to dryness while thoroughly mixing. After baking the dried soybean for 200,004 hours and 400,04 hours, water was added to soften it, and it was molded into a cylindrical shape of 2 sails x 2 sides. After drying, this was fired for 600q04 hours. Examples 2 and 4-13 Fixed bed catalysts whose empirical formulas are shown in Table 1 were prepared in a similar manner to the catalyst of Example 1.

Note that nitrates were used as raw materials for both the Rb component and the Cs component. Table 1 Example 3 The empirical formula is Mo,2 Bj6 Sb,.

Nj6 P, K, . . Na. ．． 27 074. ,(S
i02)7. A fluidized bed catalyst was prepared as follows. Silica sol (wt% of Si02 2, Na200
．． 04% by weight) was taken, and 73% of phosphoric acid (total amount 85%) was added thereto.

(1) 1.35 kg of ammonium paramolybutate was dissolved in 5 bottles of pure water and added to (1).

(0) 1.11k9 of nickel nitrate was added to (0) and mixed.

(m) 64 g of potassium nitrate was added to (m).

(W) 5 kg of nitric acid (3% by weight) and 1.5 kg of bismuth nitrate.
85k9 was added and dissolved, and this was added to (W). (V)
0.93k9 of antimony trioxide was taken, added to (V), and mixed well. This suspension was dried using a mist dryer.
It was mist-dried using a conventional method.

The generated fine 4/spherical powder was heated to 400q for 2 hours at 200°C.
It was fired for 02 hours and finally fired for 600q04 hours. This fluidized catalyst had enough strength to withstand industrial use.

Comparative Examples 1-5 Fixed bed catalysts whose empirical formulas are shown in Table 2 were prepared in the same manner as the catalyst of Example 1.

Note that in Comparative Example 3, ferric nitrate was used instead of nickel nitrate. Table 2 Test Methods and Activity Test Results The activity tests of the catalysts in Examples and Comparative Examples were carried out by the following method.

Test method A: Each catalyst is packed into a U-shaped reactor on the 16th inner diameter side for a predetermined contact time.

This is heated with a molten salt solution consisting of a mixture of equal amounts of sodium nitrite and potassium nitrate and maintained at a predetermined reaction temperature. Inject the reaction gas into this reactor for 1 hour and 7 days (NTP conversion)
supply at the rate of

Test Method B A catalyst is packed into a fluidized bed reactor with a 2-inch inner diameter and a 2-inch height in the catalyst fluidizing section.

A reaction gas is supplied into this reactor so that the apparent linear gas velocity is 15 skin/sec. Table 3 shows the catalyst activity test results using these test methods.

Note that the yield of methacrylonitrile and the contact time are defined as follows.

Methacrylonitrile yield (%) = Carbon weight XI of produced methacrylonitrile.

○ Carbon weight of supplied isobutene Note that the yields of acetonitrile and hydrocyanic acid are also calculated on a carbon weight basis, similar to the yield of methacrylonitrile.

Contact time (sec) = Apparent volume of Samenagi Table 3 Supply gas flow rate (s/sec) under reaction conditions

Claims (1)

[Claims] 1 Isobutene, oxygen and ammonia are combined using the following empirical formula Mo_1_2Bi_aSb_bNi_CP_dA_eO
__f (here, A is at least one element selected from the group consisting of Na, K, Rb and Cs, and the subscript a,
b, c, d, e, f indicate the atomic ratio of each element when Mo is 12, a = 3 to 15, b = 2 to 15,
c = 1 to 10, d = 0 to 5, e = 0.3 to 5, and f = the number corresponding to the oxide formed by combining each of the above components). A method for producing methacrylonitrile.