JPH0597431A - Production of unsaturated nitrile and hydrocyanic acid - Google Patents

Abstract

PURPOSE:To efficiently produce unsatd. nitrile and hydrocyanic acid. CONSTITUTION:When alkane is brought into a vapor phase catalytic oxidation reaction with ammonia in the presence of a metal oxide to produce unsatd. nitrile and hydrocyanic acid, one or more kinds of specified compds. selected from among methanol, acetonitrile, formaldehyde, methyl formate and dimethyl ether are fed into the vapor phase catalytic oxidation reaction zone in combination with the alkane.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing unsaturated nitriles and hydrocyanic acid. More specifically, the present invention relates to a method for increasing the yield of unsaturated nitrile and the yield of hydrocyanic acid by simultaneously supplying and reacting a specific substance when an unsaturated nitrile is produced by subjecting an alkane and ammonia to a gas phase catalytic oxidation reaction.

[0002]

BACKGROUND OF THE INVENTION Prussic acid is an important raw material in the production of acetone cyanohydrin, an intermediate for synthesizing methyl methacrylate, glycine, lactonitrile and the like. However, since hydrocyanic acid is extremely toxic to living organisms, it is impossible to transport hydrocyanic acid at sea or land, and the required hydrocyanic acid is used by using raw materials that are easy to transport and handle. We have no choice but to create a system that manufactures and consumes in the required factory.

Therefore, an ammoxidation reaction of methanol, acetonitrile and the like is known as a method for producing hydrocyanic acid (Japanese Patent Publication Nos. 60-26043 and 60-2604).
4, the same 60-26045, the same 60-26046),
The production of hydrocyanic acid alone is not an economically advantageous method unless hydrocyanic acid is stable and is consumed in large amounts. In particular, in recent years, it is much more economically advantageous to recover the cyanide produced as a by-product during the production of unsaturated nitriles, mainly acrylonitrile, and methacrylonitrile by the ammoxidation reaction of alkenes, mainly propylene, and isobutene. It is in. However, with regard to the catalyst used in this reaction, improvement studies have been vigorously pursued and the yield of unsaturated nitrile has been improved, but the amount of hydrocyanic acid produced as a by-product tends to be drastically reduced.

On the other hand, recently, a method for producing an unsaturated nitrile using a cheaper alkane as a raw material has been attracting attention. In particular, the price difference between propane and propylene, or
Due to the price difference between isobutane and isobutene, lower alkanes such as propane and isobutane are used as raw materials, and acrylonitrile and methacrylonitrile are produced by the so-called ammoxidation reaction method, in which catalytic reaction is performed with ammonia and oxygen in the presence of a catalyst in the gas phase. There is increasing interest in developing methods for producing nitriles.

[0005]

However, according to the above-mentioned method for producing an unsaturated nitrile using an alkane as a raw material, at present, the yield of unsaturated nitrile is not sufficiently satisfactory, and a small amount of hydrocyanic acid is produced as a by-product. However, there is no consideration to increase the yield of hydrocyanic acid, which has the same value added as unsaturated nitriles, without reducing the yield of unsaturated nitriles. Further, even if the catalyst used in the method for obtaining hydrocyanic acid by the ammoxidation reaction of the above-mentioned methanol, acetonitrile, etc. is used, unsaturated nitrile cannot be obtained in good yield.

[0006]

Means for Solving the Problems As a result of intensive studies made by the present inventors in view of the above problems, as a result of increasing the yield of unsaturated nitrile during production of unsaturated nitrile by ammoxidation reaction of alkane, The inventors have found a method of increasing the yield of hydrocyanic acid and have reached the present invention. That is,
The gist of the present invention is, in the presence of a metal oxide in the presence of a metal oxide, in a method for producing an unsaturated nitrile and hydrocyanic acid by performing a gas phase catalytic oxidation reaction with ammonia, in the method of alkane, methanol, acetonitrile, formaldehyde,
A method for producing unsaturated nitrile and hydrocyanic acid, which comprises supplying one or more specific substances selected from the group consisting of methyl formate and dimethyl ether to a gas phase catalytic oxidation reaction zone.

The alkane as a raw material in the present invention for explaining the present invention in detail is not particularly limited, and examples thereof include methane, ethane, propane, butane, isobutane, pentane, hexane, heptane and cyclohexane. Considering the industrial use of the resulting nitrile, it is preferable to use a lower alkane having 1 to 4 carbon atoms, particularly propane or isobutane.

According to the present invention, when an alkane is supplied to a gas phase catalytic oxidation reaction zone with ammonia, a specific substance, specifically, methanol, acetonitrile, formaldehyde,
By simultaneously supplying one or more substances of methyl formate and dimethyl ether, the yields of unsaturated nitrile and hydrocyanic acid are increased. The supply amount of these specific substances is not particularly limited as long as the reaction conditions are appropriately selected, but usually, the molar ratio to the alkane is based on carbon, usually,
0.01 to 0.3, preferably 0.03 to 0.2 (for example, when the alkane is propane having 3 carbon atoms and the specific substance is methanol having 1 carbon atom, 1 mole of methanol is equivalent to 1 mole of propane) Therefore, the molar ratio of methanol to be supplied is usually 0.03 to 0.9.
It is preferably 0.09 to 0.6. ). Even if it exceeds this range, that is, 0.3, no particular problem arises, but it is necessary to change the conventional production conditions of only unsaturated nitrile to some extent. In addition, it is recognized that the yield of hydrocyanic acid slightly decreases.

Although the details of the reaction mechanism are not clear from the above specific substances, it is presumed that some hydrocyanic acid is produced via the intermediate having 1 carbon atom due to the common structure of the specific substances. It Moreover, the presence of these specific substances and intermediates thereof is presumed to promote the production of unsaturated nitriles.

As the metal oxide used in the present invention, those generally used as known ammoxidation catalysts can be applied. Specifically, Mo-Bi-P-O based catalysts (JP-A-48-16887), V-Sb-O-based catalysts (JP-A-47-33783, JP-B-50-23016).
No.), Sb-UV-Ni-O based catalyst (Japanese Patent Publication No. 47-1).
4371), Sb-Sn-O-based catalyst (Japanese Patent Publication No. 50-2).
No. 8940), V-Sb-W-P-O based catalyst (JP-A-2
-95439), Mo-V-Te-Nb-O-based catalyst (JP-A-2-257), Mo-V-Te-Nb-X-.
O or Mo-V-Te-X-O based catalyst (X is Mg, M
Japanese Patent Application No. 3-10 showing a metal selected from n, Co, etc.
No. 4382) is exemplified.

Of these, catalysts disclosed in Japanese Patent Application Laid-Open No. 2-257 and Japanese Patent Application No. 3-104382 are 340 to 48.
The unsaturated nitrile can be obtained with a high selectivity at a relatively low temperature of 0 ° C., which is preferable.

As an example, the Mo-V-Te-Nb-O type catalyst will be further described. The catalyst has an empirical formula of Mo _1.0.
Represented by _{V a Te b Nb c O n} . In the formula, a, b, and c represent the atomic ratio of each component element to 1 atom of Mo, and a is 0.
01 to 1.0, preferably 0.2 to 0.4, b is 0.01
To 1.0, preferably 0.2 to 0.4, and c is 0.01 to
1.0 is preferably 0.1 to 0.2, and n is a number determined by the oxidation states of other elements. The method for preparing the catalyst is not particularly limited, but the following method is exemplified. In an aqueous solution containing a predetermined amount of ammonium metavanadate, an aqueous solution of tin oxalate, an aqueous solution of telluric acid, an aqueous solution of niobium ammonium oxalate and an aqueous solution of ammonium paramolybdate is used in which the atomic ratio of each metal element is a predetermined ratio. Are added sequentially in an amount ratio such that
To evaporate to dryness, and the dried product is fired at a temperature of about 350 to 700 ° C. to obtain the target metal oxide.

The metal oxide used in the present invention may be used alone, but may be used together with a well-known carrier 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. The method of the present invention is selected from the group consisting of methanol, acetonitrile, formaldehyde, methyl formate and dimethyl ether together with alkanes in the presence of a metal oxide catalyst as described above.
An unsaturated nitrile and hydrocyanic acid are efficiently produced by supplying a specific substance of at least one species and performing a gas phase catalytic oxidation reaction with ammonia.

The oxidation reaction in the present invention is carried out by oxygen atoms present in the above metal oxide or oxygen present in the feed gas. When oxygen is present in the feed gas, oxygen may be pure oxygen gas, but it is generally economical to use an oxygen-containing gas such as air because purity is not particularly required. When oxygen is not present in the supply gas, a mixed gas of alkane-specific substance-ammonia and an oxygen-containing gas are supplied alternately to prevent reductive deterioration of the composite oxide, or a moving bed type reaction. It is preferable to use a reactor to continuously feed the composite oxide to an oxidation regenerator and regenerate it for use.

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 1 to 15 mol based on propane. The ratio of ammonia supplied to the reaction is usually in the range of 0.2 to 5 mol times, and particularly 0.5 to 3 mol times the amount of propane. The reaction is usually carried out under atmospheric pressure, but it can also be carried out under slightly elevated pressure or reduced pressure. Furthermore, the gas space velocity SV in the gas phase reaction
Is usually 100 to 10,000 h ^-1 , preferably 300
It is in the range of up to 2000 h ^-1 . In addition, as a diluent gas for adjusting the space velocity and the oxygen partial pressure, nitrogen, argon,
An inert gas such as helium can be used.

The above reaction conditions are common to those of the conventional method for producing an unsaturated nitrile from an alkane which does not supply the specific substance of the present invention. The reactivity of specific substances such as methanol is much higher than that of alkanes, and it is sufficient to convert the specific substances by supplying ammonia and oxygen stoichiometrically. Therefore, in the ammoxidation of alkane, oxygen and ammonia are usually used in excess, so that it is necessary to change the conditions especially when the supply amount of the specific substance is about 0.01 to 0.3 on a carbon basis. Absent.

Further, the unreacted amount of the specific substance such as methanol is substantially zero, and it is not necessary to install new refining equipment. That is, in order to carry out the present invention, basically, it is only necessary to attach a device for supplying a specific substance such as methanol to a conventional facility for producing an unsaturated nitrile from an alkane.

[0018]

EXAMPLES The present invention will be described in more detail with reference to examples and reference examples, but the present invention is not limited to these examples unless it exceeds the gist. The analysis of the product was performed by gas chromatography. The conversion rate (%), selectivity rate (%) and yield rate (%) in the following examples and comparative examples are shown by the following equations, respectively. Alkane conversion (%) = (moles of consumed alkane / moles of supplied alkane) x 100 Selectivity of unsaturated nitrile (%) = (moles of produced unsaturated nitrile / mols of consumed alkane) x 100 Unsaturated nitrile yield (%) = (moles of unsaturated nitrile produced / moles of alkane supplied) x 100 Prussic acid yield (%) = (moles of hydrocyanic acid produced / moles of alkane fed) x (1 / X) × 100 (x represents the carbon number of the alkane.)

[0019]

Reference Example 1 Experimental An oxide having the composition Mo ₁ V _0.4 Te _0.2 Nb _0.1 O _n was prepared as follows. 4.21 g of ammonium metavanadate salt was dissolved in 117 ml of warm water,
To this, 4.13 g of telluric acid and 15.9 g of ammonium paramolybdate were sequentially added to prepare a uniform aqueous solution. Further, 21.9 g of an aqueous solution of ammonium niobium oxalate having a niobium concentration of 0.41 mol / kg was mixed to prepare a slurry. The slurry was evaporated to dryness to give a solid. 5 mmΦ x 3 mm of this solid using a tablet press
After being molded into L, it was pulverized, sieved to 16 to 28 mesh, and fired in a nitrogen stream at 620 ° C. for 2 hours.

0.5 ml of the oxide thus obtained was charged into a reactor, the reaction temperature was 430 ° C. and the space velocity SV was 10.
Fixed at 00h ^-1 , propane: ammonia: air =
Gas was supplied at a molar ratio of 1: 1.2: 15 to carry out a gas phase catalytic oxidation reaction. As a result, the propane conversion was 78.
5%, the selectivity of acrylonitrile is 59.7%,
The yield of acrylonitrile was 46.8%, and the yield of hydrocyanic acid was 4.4%.

[0021]

Example 1 A vapor phase catalytic oxidation reaction of propane was carried out in the same manner as in Reference Example 1 except that methanol was supplied. That is, propane: ammonia: air: methanol = 1:
Gas was supplied at a molar ratio of 1.2: 15: 0.24. The supply ratio of methanol to propane is 0.08 on a carbon basis. Further, since a small amount of methanol was added, the space velocity SV became 1014 h ^-1 . The reaction results at 430 ° C. were that the propane conversion was 77.7%, the acrylonitrile selectivity was 63.6%, the acrylonitrile yield was 49.4%, and the hydrocyanic acid yield was 5.6%. It was

[0022]

Reference Example 2 An oxide was prepared in the same manner as in Reference Example 1 except that the amount of the niobium ammonium oxalate aqueous solution used in Reference Example 1 was changed to 32 ° C and the firing temperature was set to 600 ° C in a nitrogen stream. The experimental composition of the obtained oxide was Mo ₁ V _0.4 Te.
A _0.2 Nb _0.15 O _n. Using the obtained oxide, a vapor phase catalytic oxidation reaction of propane and ammonia was carried out under the same conditions as in Reference Example 1 except that the reaction temperature was 420 ° C.

As a result, the propane conversion was 80.5%.
The selectivity of acrylonitrile is 57.4%, the yield of acrylonitrile is 46.2%, and the yield of hydrocyanic acid is 5.3.
It was 5.

[0024]

[Example 2] Reference example 2 except that acetonitrile was supplied
The vapor-phase catalytic oxidation reaction of propane was conducted in the same manner as in. That is, propane: ammonia: air: acetonitrile =
Gas was supplied at a molar ratio of 1: 1.2: 15: 0.075. The supply ratio of acetonitrile to propane is 0.050 on a carbon basis. Due to the addition of a small amount of acetonitrile, the space velocity SV was 1004 h ^-1 . As for the reaction results at 420 ° C, the propane conversion was 80.7% and the acrylonitrile selectivity was 58.7%.
The yield of acrylonitrile was 47.4%, and the yield of hydrocyanic acid was 5.95%.

[0025]

EFFECTS OF THE INVENTION According to the method of the present invention, in a method for producing an unsaturated nitrile by an ammoxidation reaction of alkane, unsaturated is obtained by supplying a small amount of one or more specific substances of methanol, acetonitrile, formaldehyde, methyl formate and dimethyl ether. The yield of nitrile and hydrocyanic acid can be increased.

Claims (3)

[Claims] 1. A method for producing an unsaturated nitrile and hydrocyanic acid by subjecting an alkane to a gas-phase catalytic oxidation reaction with ammonia in the presence of a metal oxide, in the method of producing an unsaturated nitrile and hydrocyanic acid, methanol, acetonitrile, formaldehyde,
A process for producing an unsaturated nitrile and hydrocyanic acid, which comprises supplying one or more specific substances selected from the group consisting of methyl formate and dimethyl ether to a gas phase catalytic oxidation reaction zone. 2. The method for producing an unsaturated nitrile and hydrocyanic acid according to claim 1, wherein the molar ratio of the specific substance to the alkane is 0.01 to 0.3 on a carbon basis. 3. The method for producing an unsaturated nitrile and hydrocyanic acid according to claim 1, wherein the alkane is propane and / or isobutane.