JPH06228073A - Nitrile manufacturing method - Google Patents

Abstract

(57) [Summary] [Structure] A process for producing a nitrile, which comprises subjecting an alkane to a gas phase catalytic oxidation reaction with ammonia in the presence of a catalyst represented by the following formula. _{W a V b Te c X x} O in _n (1) (Formula (1), X is Nb, Ta, Ti, Re, A
1, Zr, Cr, Mn, Fe, Ru, Co, Rh, N
represents one or more elements selected from i, Pd, Pt, Sb, Bi, In and Ce, where a = 1, b = 0.01 to 1.0 c = 0.01 .About.1.0 x = 0.01 to 1.0, and n is determined by the oxidation states of other elements. [Effect] Nitrile can be efficiently produced from alkane under relatively low temperature conditions of about 400 to 470 ° C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing nitrile. More particularly, it relates to an improved nitrile production method using alkane as a raw material.

[0002]

BACKGROUND OF THE INVENTION Nitriles such as acrylonitrile and methacrylonitrile are industrially produced as important intermediates for fibers, synthetic resins, synthetic rubbers and the like. The most general method is to react an olefin such as the above with an ammonia and oxygen in the presence of a catalyst in a gas phase at a high temperature.

On the other hand, due to the price difference between propane and propylene or the price difference between isobutane and isobutene, lower alkanes such as propane and isobutane are used as starting materials, and ammonia and oxygen are used in the presence of a catalyst. There is an increasing interest in the development of a method for producing acrylonitrile and methacrylonitrile by a so-called ammoxidation reaction method in which they are catalytically reacted with each other in a gas phase.

As an example of these reports, Mo-Bi-P
-O catalyst (Japanese Patent Laid-Open No. 48-16887), V-Sb-
O-based catalyst (JP-A-47-33783, JP-B-50-2)
No. 3016, JP-A-1-268668), Sb-U-
V-Ni-O catalyst (Japanese Patent Publication No. 47-14371), S
b-Sn-O type catalyst (Japanese Patent Publication No. 50-28940), V
-Sb-W-P-O catalyst (Japanese Patent Laid-Open No. 95439/1990)
No.), V-Sb-W-O-based oxide and Bi-Ce-Mo-
A catalyst obtained by mechanically mixing W—O type oxides (Japanese Patent Application Laid-Open No. Sho 6-96).
4-38051) and the present inventors
o-V-Te-Nb-O based catalyst (JP-A-2-257)
Is reported.

[0005]

However, none of these methods can sufficiently satisfy the target yield of nitriles. In addition, in order to improve the yield of nitriles, a method of adding a small amount of an organic halide, an inorganic halide, or a sulfur compound to the reaction system, a method of adding water, or the like has been attempted. There is a problem of corrosion of the reactor, and the latter has problems such as generation of a by-product by side reaction and its treatment, which are both difficult in industrial implementation.

Further, in the conventional method using a catalyst system, except for the Mo-V-Te-Nb-O catalyst and a few other examples reported by the present inventors, generally, a temperature of about 500 ° C. or higher is extremely high. Since it requires a high reaction temperature,
It is not advantageous in terms of reactor material, manufacturing cost, etc.

[0007]

Means for Solving the Problems As a result of various studies on a method for producing a nitrile using an alkane as a raw material, the present inventors have found that tungsten (W), vanadium (V), tellurium (Te) and a specific kind of metal are used. In the presence of a catalyst consisting of
By subjecting an alkane to a gas phase catalytic reaction with ammonia, it is possible to obtain a target with a significantly higher yield than the conventional method at a relatively low temperature of about 400 to 470 ° C. without the presence of halide, water, etc. in the reaction system. The inventors have found that nitriles can be produced and have reached the present invention.

That is, the gist of the present invention resides in a method for producing a nitrile, which comprises subjecting an alkane to a gas phase catalytic oxidation reaction with ammonia in the presence of a catalyst represented by the following formula. _{W a V b Te c X x} O in _n (1) (Formula (1), X is Nb, Ta, Ti, Re, A
1, Zr, Cr, Mn, Fe, Ru, Co, Rh, N
represents one or more elements selected from i, Pd, Pt, Sb, Bi, In and Ce, where a = 1, b = 0.01 to 1.0 c = 0.01 .About.1.0 x = 0.01 to 1.0, and n is determined by the oxidation states of other elements. )

The present invention will be described in detail below. The catalyst of the present invention is a composite oxide represented by the above formula (1), in which the above elements are used as X, preferably Nb, Ta, Ti and Re, and particularly preferably Nb. . Further, as a coefficient of the equation (1), when a = 1, b = 0.1 to 0.6, c = 0.05 to 0.6, x =
0.01 to 0.4 is particularly preferable.

The method for preparing the above catalyst is as follows.
Each example, in the case of _{W a V b Te c Nb x} O n, to an aqueous solution containing a predetermined amount of ammonium metatungstate salt, an aqueous solution of telluric acid, an aqueous solution of ammonium niobium oxalate salt and an aqueous solution of ammonium paramolybdate salt The metal elements are sequentially added in a ratio such that the atomic ratio of the metal elements becomes a predetermined ratio, dried by evaporation dry solidification method, spray drying method, vacuum drying method, etc. Of oxide. Further, in order to efficiently perform the firing, the dried product may be thermally decomposed at 150 to 350 ° C. in the atmosphere of air or an inert gas such as nitrogen or argon before the final firing.

The calcination is generally considered to be carried out in an oxygen atmosphere, but the catalyst used in the present invention preferably has a calcination atmosphere substantially in the absence of oxygen. For example, in an atmosphere of an inert gas such as nitrogen, argon, or helium, or hydrogen in the gas,
It may contain a reducing gas such as hydrocarbon or water vapor, or is carried out in vacuum at a temperature of usually 350 to 700 ° C., preferably 400 to 650 ° C. for usually 0.5 to 30 hours, preferably 1 to 10 hours. To be done.

The raw materials for the above oxides are not limited to those mentioned above, but WO ₃ , V ₂ O ₅ , V
Oxides such as ₂ O ₃ , TeO ₂ , and Nb ₂ O ₅ , WCl ₃ , V
A wide range of compounds can be selected such as halides or oxyhalides such as OCl ₃ and NbCl ₅ and alkoxides such as VO (OEt) ₃ and Nb (OEt) ₅ .

The above catalysts can be used alone, but can also be used together with well-known carriers such as silica, alumina, titania, aluminosilicate, diatomaceous earth and the like.
Further, it is molded into an appropriate shape and particle size depending on the scale of reaction, method, and the like. In the present invention, a nitrile can be efficiently produced by subjecting an alkane to a gas-phase catalytic oxidation reaction with ammonia in the presence of the above-mentioned catalyst.

The alkane as a raw material in the method for producing a nitrile of the present invention is not particularly limited, and examples thereof include methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, cyclohexane and the like. Considering the industrial use of the obtained nitrile, lower alkane having 1 to 4 carbon atoms, especially propane,
Preference is given to using isobutane.

Although the details of the mechanism of the oxidation reaction in the present invention are not clear, it is carried out by oxygen atoms present in the above oxide or molecular oxygen present in the feed gas. When molecular oxygen is present in the feed gas, the molecular oxygen may be pure oxygen gas, but it is economical to use an oxygen-containing gas such as air since purity is not particularly required. Alkane, a mixed gas of ammonia and an oxygen-containing gas is usually used as the supply gas, but a mixed gas of an alkane and ammonia and an oxygen-containing gas may be alternately supplied.

Further, it is also possible to carry out a gas phase catalytic reaction using only alkane and ammonia, which are substantially free of molecular oxygen, as feed gases. In such a case, a method is preferable in which a part of the catalyst is appropriately extracted from the reaction zone, the catalyst is sent to an oxidation regenerator, and after regeneration, the catalyst is re-supplied to the reaction zone. Examples of the method for regenerating the catalyst include a method in which an oxidizing gas such as oxygen, air or nitric oxide is passed through the catalyst in the regenerator usually at 300 to 600 ° C.

In the case of using propane as the alkane and air as the oxygen source, the ratio of the air supplied to the reaction is important for the selectivity of the acrylonitrile produced, and the air is Usually, the acrylonitrile selectivity is high in a range of 25 mol times or less, particularly in the case of 1 to 15 mol with respect to propane. Further, the proportion of ammonia supplied to the reaction is preferably in the range of 0.2 to 5 mole times, particularly 0.5 to 3 mole times, relative to propane. The reaction is usually carried out under atmospheric pressure, but it can also be carried out under slightly elevated pressure or reduced pressure. For other alkanes, the composition of the feed gas is selected according to the reaction conditions for propane.

In the method of the present invention, a temperature lower than that in the conventional ammoxidation reaction of alkane, for example, 34
It can be carried out at 0 to 480 ° C, particularly preferably at about 400 to 470 ° C. The gas space velocity SV in the gas phase reaction is usually 100～10000H ^-1, preferably in the range of 300~2000h ^-1. In addition,
As a diluent gas for adjusting space velocity and oxygen partial pressure,
An inert gas such as nitrogen, argon or helium can be used.

[0019]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless it exceeds the gist. The conversion rate (%) in the following examples and comparative examples,
The selectivity (%) and the yield (%) are respectively shown by the following equations.

[0020]

[Formula 1] Alkane conversion rate (%) = (mol number of consumed alkane / mol number of supplied alkane) × 100 Selectivity of target nitrile (%) = (mol number of target nitrile to be produced / mol number of consumed alkane) × 100 Yield (%) of target nitrile = (mol number of nitrile for production / mol number of alkane supplied) × 100

Example 1 A catalyst having the experimental composition formula W ₁ V _0.3 Te _0.23 Nb _0.12 O _n was prepared as follows. 23.2 g of ammonium metatungstate aqueous solution corresponding to 50% by weight as WO _3.
50 g of water was added to the mixture, then 1.75 g of ammonium metavanadate and 2.64 g of telluric acid were added to obtain a uniform aqueous solution. The niobium concentration in the aqueous solution was 0.5 mol / l
12 ml of an aqueous solution of ammonium niobium oxalate is added,
A slurry was obtained. The slurry was evaporated to dryness at about 150 ° C. to obtain a dried product. The dried product was molded into a size of 7 mmφ × 4 mmL using a tablet molding machine and then pulverized to 16 to 2
It was sieved to 8 mesh and baked at 600 ° C. for 2 hours in a nitrogen stream.

0.5 ml of the catalyst thus obtained was charged into a reactor and the reaction temperature was 450 ° C. and the space velocity SV was 500.
Fixed at h ^-1 , propane: ammonia: air = 1:
Gas was supplied at a molar ratio of 1.2: 15 to carry out a gas phase catalytic reaction. The results are shown in Table-1.

Example 2 In the same manner as in Example 1, the experimental composition formula W ₁ V _0.3 Te _0.3
Nb _0.12 O _n was prepared a catalyst with the reaction temperature 46
Table 1 shows the results of the gas phase catalytic reaction under the same conditions as in Example 1 except that the temperature was 0 ° C.

Example 3 In the same manner as in Example 1, the experimental composition formula W ₁ V _0.4 Te _{0.2 was used.}
Nb _0.1 catalysts with O _n was prepared, the reaction temperature 440
Table 1 shows the results of the gas-phase catalytic reaction carried out under the same conditions as in Example 1 except that the temperature was changed to ° C.

Comparative Examples 1 to 4 W, A composite oxide was prepared in the same manner as in Example 1 except that any one of V, Te and Nb was removed. Table 1 shows the results of the gas phase catalytic reaction under the same conditions as in Example 1 except that the reaction temperature of each oxide was set to a predetermined temperature.

Comparative Examples 5 to 7 Composite oxides containing any one of Ti, Zr and Sn components instead of the W component were prepared according to the method of Example 1. Table 1 shows the results of the gas phase catalytic reaction under the same conditions as in Example 1 except that the reaction temperature of each oxide was set to a predetermined temperature.
Shown in 1.

[0027]

[Table 1]

[0028]

EFFECTS OF THE INVENTION According to the method of the present invention, by using a new catalyst using alkane as a raw material, it is possible to prevent the presence of halides, water and the like in the reaction system, and further, 400 to 4
The target nitrile can be efficiently produced at a relatively low temperature of about 70 ° C.

Claims (1)

[Claims] 1. A process for producing a nitrile, which comprises subjecting an alkane to a gas phase catalytic oxidation reaction with ammonia in the presence of a catalyst represented by the following formula. _{W a V b Te c X x} O in _n (1) (Formula (1), X is Nb, Ta, Ti, Re, A
1, Zr, Cr, Mn, Fe, Ru, Co, Rh, N
represents one or more elements selected from i, Pd, Pt, Sb, Bi, In and Ce, and when a = 1, b = 0.01 to 1.0 c = 0.01 .About.1.0 x = 0.01 to 1.0, and n is determined by the oxidation states of other elements. )