JP3117266B2 - Method for producing methacrylonitrile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing methacrylonitrile by subjecting isobutane to gas-phase catalytic ammoxidation with ammonia and molecular oxygen.

[0002]

2. Description of the Related Art There have been proposed many catalysts for producing α, β-unsaturated nitriles by subjecting C ₃ -C ₅ paraffins to gas phase catalytic ammoxidation. Above all, a catalyst for synthesizing methacrylonitrile by ammoxidation of isobutane is 197.
Many proposals have been made since the 0s. For example, USP
U.S. Pat. No. 4,879,264 discloses a one-piece catalyst composed of V-Sb-O.
-O catalyst (former catalyst) and Bi-Fe-Cr-Mn- (N
A combination of oxidative dehydrogenation of paraffin to olefin (binary catalyst) of i-Co / Mg) -Mo-O catalyst (latter catalyst) and ammoxidation of olefin (latter catalyst) has been proposed. In addition, US Pat.
Is Cs-K-Ni-Co-Fe-Mn-Bi-Cr-M
a mono-component catalyst composed of o-O, JP-A-3-58961 discloses a catalyst having a Bi-V-Mo celite structure,
Japanese Patent Application Laid-Open No. Hei 3-58962 discloses Ga / Ta-Bi-Mo-O.
Have been proposed. In general, paraffins have lower reactivity than olefins, and therefore, conventional catalysts have low paraffin conversion under olefin ammoxidation conditions. Therefore, in the conventional catalyst, a relatively high reaction temperature is required for the ammoxidation of paraffin, and the selectivity to the unsaturated nitrile is low due to the concurrent radical reaction and the sequential oxidation of the target unsaturated nitrile. There was a problem.

[0003]

It is an object of the present invention to provide an isobutane ammoxidation catalyst having high activity and high selectivity to methacrylonitrile.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have developed an ammoxidation reaction of isobutane and a catalyst used therefor, especially Mo.
In order to develop a catalyst having excellent activity and selectivity for methacrylonitrile, a catalyst containing, as an essential component, a catalyst component, a composition and a preparation method were intensively studied.
It was found that when a catalyst containing one or more elements selected from Ta and Nb as essential components in addition to o was used, high activity and methacrylonitrile selectivity were obtained, and the process of the present invention was achieved. . That is, the present invention provides a method for producing methacrylonitrile by contacting isobutane, ammonia and molecular oxygen in a gas phase,

[0005] Formula _{XMo a A b B c C d} O p [ wherein, X is at least one element selected from Ta and Nb, A is W, Sn, Sb, Fe, Al, Cr, C
o, one or more elements selected from Ni, Cu, Mg, Ca, Sr and Ba, B is one or more elements selected from Li, Na, K, Rb and Cs, C is Ce,
Represents one or more elements selected from Pr and Tb. a, b, c, d and p are based on X,
Represents the atomic ratio of each element, a is 0.1 to 24, b is 1 to 20, c
Is 0 to 0.4, d is 0 to 0.4, and p is the number of atoms required to satisfy the valence of each component element. ] A method for producing methacrylonitrile by ammoxidation of isobutane, characterized by containing a catalyst represented by the formula:

In order to obtain the effects of the present invention, it is preferable that Bi is not contained as a catalyst component. Since multi-component composite oxide catalysts containing Mo and Bi as essential components are widely used industrially as ammoxidation catalysts for olefins, conventionally, as a paraffin ammoxidation catalyst, there are many catalysts containing Mo. In this case, Bi was regarded as an essential component. However, according to the knowledge of the present inventors, Bi is a catalyst component in the present catalyst containing, as an essential component, at least one element selected from Ta and Nb in addition to Mo. Is not preferred, because the catalytic activity decreases.

The catalyst used in the method of the present invention can be prepared by a known method usually used in this field, for example, the following method. After heating and dissolving ammonium molybdate in pure water and neutralizing by adding a nitric acid aqueous solution, adding tantalum oxide, and stirring this at about 100 ° C.,
Heat under reflux and, if necessary, W, Sn, Sb, Fe,
A compound of at least one element selected from the group consisting of Al, Cr, Co, Ni, Cu, Mg, Ca, Sr and Ba, for example, a nitrate salt is added, and if necessary, a carrier such as SiO ₂ is added. , Drying and calcining the resulting muddy suspension,
It is prepared by firing.

The starting material for the catalyst of the present invention is preferably a compound which can be decomposed into an oxide during the preparation of the catalyst. Examples of such compounds include oxides, hydroxides, nitrates, ammonium salts, carbonates, chlorides, organic acid salts, metal acids, and ammonium metal salts. As raw materials for SiO ₂ ,
Silica sol, silica gel, silicates, silicates and the like are used. The catalyst is used in a fixed bed as a granular or shaped body, but can also be used as a moving bed or a fluidized bed. Isobutane, ammonia, and molecular oxygen are used as a raw material gas for the gas phase catalytic oxidation reaction according to the present invention. A diluent gas can be used in addition to these raw material gases.

Air is usually used as the molecular oxygen source, but pure oxygen may be used. As a diluting gas, an inert gas such as nitrogen or carbon dioxide is used. A part of the non-condensable gas contained in the reaction gas may be circulated and used as a diluent gas. It is preferable to use water vapor as the diluent gas in order to enhance the activity and selectivity. The composition of the raw material gas is not particularly limited, but from the viewpoint of safety, the composition of the mixed gas is preferably out of the combustion range.
When steam is also used as the diluent gas, the steam in the raw material gas is usually added up to 60% by volume. In the gas phase catalytic oxidation reaction according to the present invention,
A temperature range of 350 to 550 ° C., normal pressure to
It is carried out by introducing at a pressure of 10 atm and a space velocity of 300 to 5000 / hr.

[0010]

The present invention will be described in more detail with reference to Examples and Comparative Examples. The conversion, selectivity and yield are defined as follows. (Mole number of reacted isobutane) Reaction rate = ────────────── × 100 (Mole number of supplied isobutane) (Mole number of generated methacrylonitrile) Selectivity = ── ───────────────── × 100 (moles of reacted isobutane) (moles of methacrylonitrile generated) Yield = ────────── ───────── × 100 (mole number of supplied isobutane)

Example 1 Ammonium heptamolybdate was dissolved in distilled water to obtain solution A. Liquid B was prepared by dissolving iron nitrate and cobalt nitrate in distilled water so that the atomic ratio of Fe / Co became 3/7. Fe / Mo
Solution B was added to Solution A such that the atomic ratio of was 3/12. An aqueous ammonia solution was added to the mixture to adjust the mixture to neutrality, and then tantalum oxide was added to the mixture so that the Ta / Mo atomic ratio became 1/12. The mixture was heated and refluxed at about 100 ° C. for 16 hours with stirring. , Evaporated to dryness. The solid obtained is 3
Calcination was performed at 40 ° C. for 4 hours and then at 600 ° C. for 4 hours in an air atmosphere to obtain a catalyst having a composition of Ta ₁ Fe ₃ Co ₇ Mo ₁₂ O _x . The performance of the obtained catalyst was evaluated. The results are shown in Table 1.

Example 2 In the same manner as in Example 1, Ta ₁ Fe ₃ Mg ₇ Ce _0.05 Mo ₁₂
A catalyst having a composition of O _x was obtained. The performance of the obtained catalyst was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0013] Comparative Example 1 Ta ₂ O ₅ and H ₂ MoO ₄ was added in distilled water to Ta / Mo atomic ratio is 2/3, stirring for 16 hours at about 100 ° C., after heating under reflux, evaporated Dried. The solid obtained is 6
Fired at 00 ° C. for 4 hours in an air atmosphere to obtain Ta ₂ Mo ₃ O ₁₄
A catalyst having the following composition was obtained. The obtained catalyst was charged into a usual flow-type reactor, and a raw material gas having a molar ratio of isobutane / oxygen / ammonia of 3/2/2 was supplied at a space velocity of 3600.
/ Hr. While maintaining the reaction temperature at 470 ° C., the performance of the catalyst was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

Comparative Example 2 Ammonium heptamolybdate and ammonium vanadate were dissolved in distilled water so that the V / Mo atomic ratio became 1/2, and neutralized by adding an aqueous nitric acid solution.
/ Mo Atomic ratio becomes 1/1, tantalum oxide is added, and the mixture is heated and refluxed at about 100 ° C. for 16 hours with stirring.
Evaporated to dryness. The obtained solid is calcined at 340 ° C. for 4 hours, and then calcined at 600 ° C. for 4 hours in an air atmosphere.
to obtain a catalyst of a ₂ V ₁ Mo ₂ O _x a composition. The performance of the obtained catalyst was evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

Comparative Example 3 A catalyst having a composition of Nb ₂ Mo ₃ O ₁₄ was obtained in the same manner as in Comparative Example 1 except that Nb was used instead of Ta. The performance of the obtained catalyst was evaluated in the same manner as in Comparative Example 1, except that the reaction temperature was changed to 440 ° C. The results are shown in Table 1.

Comparative Example 4 Ammonium heptamolybdate was dissolved in distilled water to obtain solution A. Bismuth nitrate and nitric acid were dissolved in distilled water to obtain solution B.
Solution B was added to Solution A such that the Bi / Mo atomic ratio was 2/3. An aqueous ammonia solution was added to the mixed solution to adjust the mixture to neutrality, and then tantalum oxide was added to the mixture so that the Ta / Mo atomic ratio became 2/3.
After heating at reflux for 6 hours, it was evaporated to dryness. The obtained solid is calcined at 340 ° C. for 4 hours, and then at 600 ° C. for 4 hours.
The catalyst was fired in an air atmosphere to obtain a catalyst having a composition of Ta ₂ Bi ₂ Mo ₃ O _x . The performance of the obtained catalyst was evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0017]

[Table 1]

[0018]

The ammoxidation catalyst used in the present invention has high activity and high selectivity to methacrylonitrile.
According to the method of the present invention, methacrylonitrile can be efficiently produced from isobutane.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C07C 253/24 C07C 255/08 C07B 61/00 300

Claims (1)

(57) [Claims] 1. Isobutane, ammonia and molecular oxygen
In the gas phase to produce methacrylonitrile
In the method, the general formula XMo_aA_bB_cC_dO_p  [In the formula, X is one or more kinds selected from Ta and Nb.
The element A is W, Sn, Sb, Fe, Al, Cr, Co,
Selected from among Ni, Cu, Mg, Ca, Sr and Ba
One or more atoms, B is Li, Na, K, Rb and Cs
At least one element selected from the group consisting of Ce, Pr, and
And one or more elements selected from Tb. a,
b, c, d and p are the origins of each element with respect to X.
A is 0.1 to 24, b is 1 to 20, c is 0
~ 0.4, d is 0 ~ 0.4, and p is the source of each component element.
This is the number of atoms required to satisfy the valence. ]
Methacrylate characterized by using a catalyst containing a product
Method for producing lonitrile.