JPS6186416A - Production method of hydrocyanic acid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing hydrocyanic acid by reacting acetonitrile with oxygen and optionally ammonia in the presence of a catalyst in the gas phase.

When producing acrylonitrile (IJ) in the gas phase from propylene, ammonia, and oxygen or an oxygen-containing gas, hydrocyanic acid and acetonitrile are produced as by-products. Hydrocyanic acid has a wide range of uses as a cooling agent, whereas acetonitrile has narrow uses and its industrial value is low.

Therefore, converting acetonitrile into hydrocyanic acid is of great industrial significance.

[Prior art and its problems]

Conventional methods for producing hydrocyanic acid from acetonitrile include:
■ Acetonitrile and ammonia in the presence of a platinum group metal catalyst without oxygen coexisting at 1ioo-%-7・'100℃
(Tokukosho/I If-/Da560)
■A method of reacting acetonitrile with oxygen and optionally ammonia in the gas phase at a temperature of q00 to 500℃ in the presence of an oxide catalyst. ■A method of reacting acetonitrile, ammonia, and oxygen at a temperature of 70℃ in the presence of a platinum/alumina catalyst or a platinum catalyst.
Method of reacting at 0-100℃ (Industrial Chemistry Magazine Volume 6g-
(pages koj3 to λg6) are known.

Method (2) is a method in which the reaction is carried out in a short contact time of 0,0/~O,S seconds.
yield? This method is noteworthy in that it shows a high yield of around ff% and can obtain a high space and time yield (hereinafter referred to as space-time yield), but because it is a high temperature reaction with a reaction temperature of 7000 ° C. This method cannot be said to be industrially advantageous in terms of equipment or energy balance.

Further, as the method (■), for example, a method using a catalyst mainly composed of iron and antimony (%Koaki &9-.330J9),
Method using a catalyst consisting of molybdenum-iron-alkali metal
oo) etc.

These methods are more attractive than method (2) in that they can produce hydrocyanic acid at a lower temperature, but they are still not sufficient in terms of space-time yield.

Method (2) is different from method (2).The method (2) is a method in which the reaction is carried out at a low temperature with a contact time of around O,OS seconds, and is a method worth noting in that a relatively high space-time yield can be obtained. The reaction yield decreases due to the volatilization of platinum and the decrease in the strength of the catalyst, and it cannot be said to be practical in terms of the life of the melting medium.

[Means for Solving the Problems] The present inventors have made extensive studies on catalysts that efficiently convert acetonitrile to hydrocyanic acid.

The inventors have discovered that hydrocyanic acid can be stably produced using an alloy catalyst consisting of platinum and rhodium with a longer life, shorter contact time, and higher space-time yield than when platinum is used alone, and the present invention has been achieved based on this finding.

That is, the purpose of the present invention is to react acetonitrile with oxygen and optionally cyanmonia in the gas phase to stably produce hydrocyanic acid with a high space-time yield. This is achieved by protecting the body.

The present invention will be explained in detail below.

The platinum-rhodium alloy catalyst used in the method of the present invention is a catalyst used for producing nitrogen oxide by oxidizing ammonia and producing hydrocyanic acid from methane and ammonia.
Its preparation is described in US Pat. No. 70 &, O35.

Platinum-rhodium alloys with a rhodium content of up to 20% by weight are preferred, and the catalyst is preferably in the form of a gauze, that is, a net or layers of nets.

Fill the above catalyst into a fixed bed reactor and set the reaction temperature to left QO-g.
The temperature is maintained at 00''C, and a mixed gas containing acetonitrile, oxygen or oxygen-containing gas, and ammonia is brought into contact with the sample.

The raw material acetonitrile does not necessarily have to be of high purity. It may contain hydrogen.

Air is used industrially as the oxygen-containing gas.

The molar ratio of oxygen to acetoni I-+ful is in the range of O,S to λ times, preferably in the range of O,S to 5 times.

When adding ammonia, the molar ratio of ammonia to acetonitrile is selected within the range of 1:1.

The reaction is usually carried out at around normal pressure, but if necessary, the contact time between the reduced material gas and the catalyst is appropriately selected from the range of 0.0θ7 to 0.0/sec.

Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

In addition, in the following examples, the reaction rate of acetonitrile, hydrocyanic acid selectivity, and hydrocyanic acid yield are defined by the following formula.

Ayato = 1 formation, 6 ratio (1) - μ (i Wataru! Su 1 work j Self = = 1 man 2 animals same customer A reaction tube made of 5US-JlOB was inserted vertically into a tube furnace made of the same material with an inner diameter of 6S, and a Pt-101Rh wire with a wire diameter of θ, 074wm1.
Layers of wire mesh made of alloy were stretched over each other. In addition, a preheater installed at the top of the reaction tube is used.

A mixed gas of acetonitrile, air, and ammonia preheated to ℃ was supplied at a predetermined rate.

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 the reaction results after 20 hours under each reaction condition.

This shows that, according to the method of the present invention, hydrocyanic acid can be efficiently produced at a relatively low temperature and for an extremely short contact time.

Example/lI The reaction was continued under the same conditions as in Example. The results after 200 hours are also shown in Table 7.

No damage or weight loss was observed on the Pt-Rh wire mesh catalyst after the reaction was completed.

Example/S Part of the raw material acetonitrile is replaced with methane.

The same experiment as in Example 7 was repeated except that a mixed gas of acetonitrile and methane in a molar ratio of 3:3 was supplied.

As a result, the conversion rates of acetonitrile and methane at a reaction temperature of 610°C are octopus, ol, tg, and ogb, respectively.
Hydrocyanic acid yield was KO, g, 73. It was θchi.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - (1 other person)

Claims (1)

[Claims] (1) A method for producing hydrocyanic acid by reacting acetonitrile with oxygen and optionally ammonia in the presence of a catalyst in the gas phase, the method comprising using a platinum-rhodium alloy as the catalyst.