DE1173444B - Process for the production of hydrogen cyanide - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Kl .: C Ol c

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German class: 12 k -3/02

J 20285IV a / 12 k
June 21, 1961
July 9, 1964

The German patent application 117671 IVa / 12 k (German Auslegeschrift 1163 304) relates to a process for the production of hydrogen cyanide by converting a mixture consisting essentially of ammonia, one or more hydrocarbons, in particular methane and oxygen, in the gas phase at a high temperature over a catalyst of a platinum metal or a platinum metal alloy in the presence of sulfur compounds, a volatile sulfur-containing material being added to the reaction mixture in an amount of 1 to 500 mg sulfur / m ³ . In this method of the main patent, the catalyst can consist, for example, in the form of several layers of a gauze made of a platinum metal or the platinum metal can be applied in the form of a surface layer on a lumpy refractory material.

It has now been found that an essential advantage can be achieved in that the catalyst, immediately before its use, by passing over a mixture consisting essentially of ammonia, one or more hydrocarbons, in particular methane and oxygen, at temperatures of 700 to 1250 ° C. at least 1 Is activated for hours, the mixture containing a sulfur-containing material in an amount of 2 to 200 mg S / m ³ .

It is known that when a gauze catalyst is used for the production of hydrocyanic acid initially a start-up period under working conditions until the maximum catalytic level is reached Activity is required. This time can take up to 5 days, during which time the conversion takes place the reactants in hydrocyanic acid are lower than in normal production and slowly increases. This activation time for a gauze catalyst can be a few hours be reduced if the reactants are regulated according to the invention during activation Quantities of a volatile sulfur-containing material can be added. When the gauze catalyst on has been activated in this way, an improved catalytic effect is obtained even if the The supply of sulfur-containing material is switched off.

Quantities smaller than 2 mg sulfur / m ^{3 of} the reaction mixture do not give the desired rapid activation of the catalyst. Amounts of sulfur greater than 200 mg / m ³ do not increase the rate or the extent of activation; much larger quantities, for example those in the larger process for the production of hydrogen cyanide

Addition to registration: 117671IV a / 12 k -
Interpretation document 1163 304

Applicant:

Imperial Chemical Industries Ltd., London

Representative:

Dr.-Ing. H. Fincke, Dipl.-Ing. H. Bohr

and Dipl.-Ing. S. Staeger, patent attorneys,

Munich 5, MüUerstr. 31

Named as inventor:

John Benjamin Warren, Widnes, Lancashire

(Great Britain)

Claimed priority:
Great Britain of July 25, 1960 (25 783),
dated July 7, 1961

are than about 500 mg sulfur / m ³ , result in no activation and appear to poison the catalyst. Therefore, the inventor uses volatile sulfur-containing material in the range of 2 to mg sulfur / m ^{3 of} the reaction mixture.

By the term "platinum metal or platinum metal alloy gauze" is meant platinum metal or an alloy be understood, which contains at least about 50% platinum metal, for example an alloy, Consists of 90% platinum and 10% rhodium, whereby the metal is present in a permeable structure, like woven wire gauze or foil with many holes.

The preferred sulfur-containing material is carbon disulfide, since this causes the catalyst activation with very small additions, but other volatile sulfur-containing substances, both organic and inorganic compounds, can be used, for example thiophene, mercaptans such as methyl, ethyl, propyl and Butyl mercaptans, thioethers such as dimethyl and diethyl sulfide and hydrogen sulfide.
It is known to use oxygen or air as the source of oxygen in the catalytic production of hydrocyanic acid, and it has been found that the rapid activation process of the invention

409 629/322

Finding is applicable to both oxygen and air systems.

The hydrocarbon component of the activation mixture is usually methane or Mixtures of methane with a smaller amount of its homologues, such as ethane, propane and butane applied, for example, the lower paraffin hydrocarbons, which are made from natural gas or from the gases produced in petroleum refining.

In practicing the process of the invention, the volume ratio of hydrocarbon to ammonia in the reaction gases expediently in the range from 0.7: 1 to 1.8: 1 and preferably in the range from 0.7: 1 to 1.4: 1. The volume ratio of oxygen to ammonia in the reaction gases is expediently in the range from 0.7: 1 to 1.3: 1 when using oxygen itself will and in the range of 0.8: 1 to 1.8: 1 when air is used as an oxygen source.

In the above-mentioned preparation of hydrocyanic acid while passing an im a mixture consisting essentially of ammonia, hydrocarbons and oxygen via a platinum metal or platinum metal gauze catalyst at high temperature, it is known the catalyst temperature to be kept in the range of 700 to 1250 ° C during normal operation. The optimal temperature depends to some extent on the composition of the feed gases but usually at 1000 ° C. Under the same temperature conditions the activation according to the invention is also carried out, i. H. that in general is activated at about 1000 ° C.

During the activation, too, the O ₂ content of the starting gas mixture must be adjusted in such a way that optimum conversion is achieved. With an activation time of 5 days, which was previously necessary, this leads to difficulties. In operating in accordance with the present invention, the duration of the catalyst activation is reduced to a few hours, usually 1 to 2 hours. In this way, the process of the present invention avoids the need for the troublesome adjustment of the oxygen content of the reactants for several days and increases production by achieving the optimum conversion much more quickly.

Most suitably, the invention is carried out in such a way that the catalyst between the activation process and the known production of hydrocyanic acid, following activation is not allowed to cool. For example, the fresh catalyst are introduced into an ordinary apparatus for the production of hydrocyanic acid, and a reaction mixture consisting of ammonia, a hydrocarbon such as methane, and oxygen, which contains the desired amount of volatile sulfur-containing material can be passed through the catalyst at a catalyst temperature of nearly 1000 ° C for at least 1 hour and usually 1 to 2 hours be directed. During the activation time, the oxygen content of the reaction mixture is adjusted so that that maximum conversion of ammonia to hydrocyanic acid is obtained, such as is determined by analyzing the gas products. At the end of the activation time, when the converting action of ammonia to hydrocyanic acid occurs Has reached the maximum, the supply of sulfur-containing material to the reactants can be maintained will. The catalytic production of hydrocyanic acid can also at high Effect to be continued with essentially sulfur-free reactants.

The invention is further illustrated by the following examples.

example 1

A sulfur-free hydrocarbon gas, consisting of approximately 70% methane and 30% hydrogen, was _{mixed with ammonia gas to a C: NH 3} ratio of 1: 1, based on the volume of the hydrocarbon and ammonia content, and was converted by passing it over Mixture with oxygen at a constant speed of almost 0.9 m / sec (based on gases at 20 ° C and 760 mm mercury column) over a 7-layer 90/10 platinum-rhodium alloy wire gauze catalyst. The oxygen content of this starting mixture was 26% and the working temperature about 1000 ° C; a maximum conversion of ammonia to hydrocyanic acid of 61% was obtained.

The initial conversion of 61% with sulfur-free reactants increased to 69-70% over the course of 2 hours when carbon disulfide was added at 5 mg S / m ^{3 of} the feed gas. Then the addition of carbon disulfide was continued in one attempt and the carbon disulfide turned off in the other attempt. In both cases the conversion of ammonia to hydrocyanic acid remained 69 to 70 percent; in this way it was found that the initial addition of the sulfur compound actually has an activating effect on the catalyst.

Example 2

A 7-layer 90/10 platinum-rhodium alloy gauze catalyst was used to catalytically produce hydrocyanic acid from a sulfur-free reaction mixture as in Example 1, but replacing the oxygen addition with air. The reaction mixture contained 67% air before carbon disulfide was added. The initial conversion of ammonia to hydrocyanic acid increased from about 40% to 62% when carbon disulfide was added to the reactant stream at 20 mg sulfur / m ³ of total feed gases. After adding the carbon disulfide, the proportion of air was increased to 68% in order to achieve an optimal conversion. After 2 hours the supply of carbon disulfide was turned off. Thereafter, the ammonia conversion efficiency was found to be 58%.

Claims (5)

Patent claims: 1. Process for the production of hydrogen cyanide according to German patent application 117671 IVa / 12 k (German Auslegeschrift 1163 304) by converting an essentially ammonia, one or more hydrocarbons, in particular methane and oxygen, existing mixture in the gas phase, at high Temperature at a catalyst made of a platinum metal or a platinum metal alloy in Presence of sulfur compounds, where a volatile sulfur-containing material is added to the reaction mixture in an amount of 1 to 500 mg sulfur / m ³ , characterized in that the catalyst is passed over a mixture consisting essentially of ammonia, one or more hydrocarbons, in particular methane and oxygen immediately before use is activated at temperatures of 700 to 1250 ° C for at least 1 hour, the mixture containing a volatile sulfur-containing material in an amount of 2 to 200 mg S / m ³ . 2. The method according to claim 1, characterized in that the catalyst corresponds to the above Subjected to activation procedures for 1 to 2 hours will. 3. The method according to claim 1 and 2, characterized in that the volatile sulfur-containing Material carbon disulfide is used. 4. The method according to claim 1 to 3, characterized in that the oxygen is supplied as air will. 5. The method according to claim 1 to 4, characterized in that the activation of the catalyst is carried out at about 1000 ° C. 409 629/322 6.64 © Bundesdruckerei Berlin