JPS61111913A - Production of hydrocyanic acid - Google Patents

Abstract

PURPOSE:To produce hydrocyanic acid in high yield at a lower reaction temperature than conventional process, by reacting a mixture of acetonitrile and a saturated hydrocarbon with oxygen and ammonia in vapor phase in the presence of a catalyst consisting of platinum or platinum and rhodium. CONSTITUTION:Hydrocyanic acid is produced by reacting a mixture of acetonitrile and a saturated hydrocarbon with oxygen and ammonia in vapor phase in the presence of a catalyst consisting of platinum or platinum and rhodium. The ratio of the oxygen to the raw material mixture is 0.5-2 times, preferably 0.8-1.2 times the theoretical value calculated by the formula (alpha is molar fraction of acetonitrile in the mixture of acetonitrile and hydrocarbon). The ratio of the ammonia to the raw material mixture is <=2 times the above theoretical value.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an industrial method for producing hydrocyanic acid.

Specifically, it relates to a method for producing hydrocyanic acid by reacting a mixture of acetonitrile and a saturated hydrocarbon with oxygen and ammonia in the presence of a catalyst in the gas phase.

[Prior art and its problems]

When acrylonitrile is produced in the gas phase from propylene, ammonia, and oxygen or acid-containing gas, hydrocyanic acid and acetonitrile are produced as byproducts. Hydrocyanic acid has wide uses as an industrial raw material, whereas acetonitrile has narrow uses and its industrial value is low. Therefore, converting acetonitrile into hydrocyanic acid is of great industrial significance.

The conventional method for producing hydrocyanic acid from acetonitrile is ■
A method of reacting acetonitrile and ammonia at ttoo-iqoo°C in the presence of a platinum group metal catalyst without the coexistence of oxygen (Special Show or-tlIsbo), ■ Temperature in the presence of an oxide catalyst: A method of reacting acetonitrile with oxygen and optionally ammonia in the gas phase at r00°C (Published in Showa Sφ-rittoo), ■Platinum/alumina catalyst,
Alternatively, a method is known in which acetonitrile, ammonia, and oxygen are reacted at a temperature of 700 to 100° C. in the presence of a platinum catalyst (Industrial Chemistry Magazine, Vol. 6g, No. 2, pages g3 to g6).

On the other hand, methods for producing hydrocyanic acid from lower saturated hydrocarbons such as methane include the Andrusmaw method and 8eh
■Many proposals have been made, including the Nigan method and the BMA method.

All reactions using these lower hydrocarbons as raw materials /θ
The drawback is that it requires a high temperature higher than OOC. Although it is known to produce hydrocyanic acid using acetonitrile and methane individually, it is completely unknown to produce hydrocyanic acid from a mixture containing both acetonitrile and lower saturated hydrocarbons such as methane. Not yet. This is because acetonitrile and lower saturated hydrocarbons such as methane have different reactivities, and conventional catalysts for producing hydrocyanic acid from acetonitrile have too low oxidation activity for lower saturated hydrocarbons such as methane, making them unsuitable. However, a major drawback was that the catalyst used to produce hydrocyanic acid from lower saturated hydrocarbons such as methane had too high oxidizing activity for acetonitrile.

By using a mixture of acetonitrile and a lower saturated hydrocarbon such as methane as a raw material, the present inventors have demonstrated that 1. ．． 00
The present invention has been accomplished by discovering that a high conversion rate can be achieved even for hydrocarbons that were conventionally thought to be inert at temperatures of about 700° C., and that the objective can be achieved.

That is, an object of the present invention is to provide a method for efficiently producing hydrocyanic acid with a high space-time yield using a mixture of acetonitrile and a saturated hydrocarbon as a raw material, and this object is to provide a method for efficiently producing hydrocyanic acid with a high space-time yield. This is achieved by reacting a mixture of acetonitrile and a saturated hydrocarbon with oxygen and ammonia in the gas phase 2 in the presence of acetonitrile and a saturated hydrocarbon.

In the method of the present invention, metallic platinum or an alloy of platinum and rhodium is used as a catalyst consisting of platinum or platinum and rhodium, and these catalysts are known as catalysts used for the production of nitrogen oxide by oxidation of ammonia. For example, the manufacturing method is disclosed in the US patent t70&0! ! listed in the number.

When using a platinum-rhodium alloy catalyst as a catalyst,
Platinum-rhodium alloys with a rhodium content in the catalyst of from 2 to 0% by weight are preferred.

The catalyst is preferably in the form of a gauze, that is, a network or a layered network.
-o-is: The diameter of the mesh, platinum or platinum-rhodium alloy wire is preferably 0.05 to 0.09 m.

The above catalyst was packed into a fixed bed reactor and the reaction temperature was set at 200-1.
The temperature is maintained at 00°C, and acetonitrile is brought into contact with a mixed gas containing a lower saturated hydrocarbon such as methane, oxygen or an oxygen-containing gas, and ammonia. The raw material acetonitrile does not necessarily have to be highly pure, and may contain aliphatic nitriles such as acrylonitrile and propionitrile, carbonyl compounds such as acetone, acrolein, and acetaldehyde, and even hydrocarbons such as propylene.

The saturated hydrocarbon which is a raw material used together with acetonitrile is preferably a saturated hydrocarbon having a carbon number of 7%/4 g in the molecule, and examples thereof include methane, ethane, purone, and butane.

Furthermore, these hydrocarbons do not necessarily have to be pure products, and may be a mixture of several types.

The ratio of acetonitrile to saturated hydrocarbon in the raw material is not particularly limited, but from the purpose of the present invention, the preferred range is /: 0.0 / to /: 10 in terms of molar ratio.

Industrially, air is preferably used as the oxygen-containing gas.

The theoretical amount of oxygen to be supplied to the raw material mixture can be calculated using the following formula, but it is in the range of 0.05 to 2 times the theoretical amount, preferably 0.005 to 2 times the theoretical amount. Selected from the range of g to box times.

αCHsCN+(/-a)CnHm+tmo[α+(n+
o, s ) (-α)) O1+ [α0m(/-a))
NH8→ (koα+1(/<)lHCN+2[α+(n
+o, r) (/-a) ]HtO(1) (where α is the molar fraction of acetonitrile in the raw material mixture of acetonitrile and hydrocarbon) The supply ratio of ammonia to the raw material mixture is also shown in equation (1). It is selected within a range up to one times the theoretical amount.

The reaction is usually carried out near normal pressure, but may be carried out under reduced pressure or increased pressure if necessary.

The contact time between the raw material gas and the catalyst is 0.00 /~O1θ/
Appropriately selected from the range of seconds.

〔Example〕

Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples unless it exceeds the scope of the invention.

In the following examples, the reaction rate of acetonitrile, the reaction rate of saturated hydrocarbons, the selectivity of hydrocyanic acid, and the yield of hydrocyanic acid are defined by the following equations.

Example t~3 A reaction tube made of 5US-, 3108 with an inner diameter of /jam is vertically inserted into a tube furnace made of the same material and with an inner diameter of jjm, and a wire diameter of 0.0? A vmφ, 10 mesh Pt-
Q pieces of wire mesh made of 10% Rh alloy were stacked and stretched. To this, a preheated mixed gas of acetonitrile, methane, ammonia, and air was supplied to the yooc at a predetermined flow rate using a preheater provided at the top of the reaction tube.

The reaction was carried out at normal pressure, and the reaction temperature was measured with a thermocouple inserted directly below the catalyst bed.

Table 1 shows the reaction conditions and reaction results.

Examples D-T The same experiment as in Example 1 was repeated except that ethane, propane, and butane were used in place of methane, respectively.

Table 1 shows the reaction conditions and reaction results.

Comparative Example The following catalyst was prepared by the method described in Japanese Patent Application No. 3G-790AAJ.

20% by weight silica gelco O under stirring? 1 mol of iron/
An aqueous solution of ferrous nitrate ("(NOs)s・'HtO) of 7.7 j mt and 1 mol/l of phosphoric acid [as phosphorus]
Aqueous solutions q and -9td of H, PO, :) were sequentially added.

Then vanadium pentoxide (V, 05) 9.099 f
water 30- and oxalic acid [(C00H),・CoH,O]2
θ% Mix, heat to dissolve, and dilute with water in a volumetric flask for 10
0tnt to prepare a 1 mol/l solution as vanadium. tA- was added to the above solution to adjust the pH of the solution to C, C, and the mixture was heated on a hot plate with stirring to dryness. '4 The solid material has a diameter of Am and a thickness of 3-
The mixture was molded into a tablet and baked at tro°C for one hour under air circulation.

The composition of the catalyst thus obtained was F@. . v61P
The ratio of the catalyst component to the silica as a carrier was 1:0 by weight.

This catalyst l- was filled in a heat-resistant glass reaction tube with an inner diameter ettax, and a mixed gas having the composition of Example-
0 hr-' (g seconds to contact time) was fed into the reaction tube, and the reaction was run at usoc.

As a result, the conversion rate of acetonitrile was 99.6%, the conversion rate of methane was u%, the selectivity of hydrocyanic acid was 7 L co%, and the yield of hydrocyanic acid was +o.r%.

Note that the above catalyst gave a hydrocyanic acid yield of t/0% at the same space velocity and the same reaction temperature when the feedstock was acetonitrile alone.

〔Effect of the invention〕

The present invention is characterized in that a mixture of acetonitrile and saturated hydrocarbons is used as a raw material, and compared to the case where only acetonitrile, which is a by-product during the production of acrylonitrile, is used as a raw material, saturated hydrocarbons, which are abundantly available, can be used at the same time. There are fewer restrictions on the availability of raw materials for use, and on the other hand, hydrocyanic acid can be obtained in higher yields at lower reaction temperatures (compared to methods using only saturated hydrocarbons as raw materials).

Note that when propane or n-butane is used as the saturated hydrocarbon, the yield of hydrocyanic acid is lower than when methane or ethane is used.
When propane or butane is used as a raw material in known techniques such as Tco3, the yield of hydrocyanic acid based on carbon weight is 21-2.
? The present invention far exceeds these known techniques.

1 other person

Claims (1)

[Claims] (1) A method for producing hydrocyanic acid, which comprises reacting a mixture of acetonitrile and a saturated hydrocarbon with oxygen and ammonia in the gas phase in the presence of a catalyst consisting of platinum or platinum and rhodium.