DE1190445B - Process for the production of hydrogen cyanide and nitriles - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

uuic

German KL: 12 k-3/02

Number: 1190 445

File number: Z 9693 IV a / 12 k

Filing date: September 29, 1962

Opening day: April 8, 1965

It is known to use mixtures of ammonia and lower hydrocarbons, such as methane, propane, Propylene, with atmospheric oxygen on platinum or platinum-rhodium gauzes and other catalysts to convert partial oxidation into hydrogen cyanide or nitriles. To achieve good yields Hydrocyanic acid or nitriles, it is necessary that as homogeneous a mixture as possible is fed to the reactor will. A complete mixture of the hydrocarbons with the oxidizing gas, i. H. with Air, or oxygen-enriched air, is technically difficult to carry out as with If these components are mixed, an area must always be traversed in which explosions or deflagrations are possible may occur. The upper explosion limit of mixtures of air with methane, propane, Propylene or other lower hydrocarbons are reduced by adding ammonia, but not up to the lower explosion limit, so that in the preparation of the for the synthesis of Hydrogen cyanide or nitriles required mixtures in all cases of the explosion range Mixture must be stepped through.

It is known that the components can be mixed in such a way that first the hydrocarbons intimately mixed with ammonia in the optimal ratio for the synthesis and this Mix then in a further mixing device the entire required amount of the oxidizing Gas were added, which can be done, for example, directly in front of the networks. With this one known methods, there may be fluctuations in the composition of the gas mixture and local The networks are overheating. If there are major irregularities in the mixture composition Deflagrations can even occur, which then damage the networks. As is well known the surface of the changes during the catalytic production of hydrogen cyanide and nitriles Platinum. The networks then give better yields, but suffer considerably in terms of their mechanical properties Properties and are then against fluctuations in the gas composition and resulting Deflagrations and local overheating are particularly sensitive.

According to the invention, the aforementioned disadvantages are avoided by adding the oxidizing gas or the oxygen-enriched air in two or more stages to the intimate mixture of ammonia and hydrocarbons in the optimal ratio for the synthesis. The addition of the oxidizing gas in the individual stages of the process for the production of hydrogen cyanide
and nitriles

Applicant:

Hans J. Zimmer Process Engineering,

Frankfurt / M., Borsigallee 1-7

Named as inventor:

Dipl.-Chem. Dr. phil. Leonid Andrussow, Paris

expediently follows tangentially, for example through nozzles or the like. If, for example, a mixture is used from ammonia and methane, instead of the full amount required for the synthesis, initially only about half of it is added, there is the risk of local occurrence of explosive or deflagration-prone Mixtures significantly reduced. The mixture obtained in this way is about 18% Methane again well above the explosion limit, and also the addition of the remaining still required The amount of oxidizing gas can therefore take place much more quickly and safely. In the inventive multi-stage addition of the oxidizing gases can be the last addition to the generator, so immediately in front of the network. It is advisable to add all or only of the gas to be added to preheat the partial stream supplied in one stage. This preheating can, for example by heat exchange with exhaust gases, for example the exhaust gases of the present synthesis.

In the case of propylene, the addition of steam is recommended for partial oxidation, since it makes it easier to maintain the optimal temperature.

In the case of propylene, the addition of air according to the invention proves to be in two or more stages a well-mixed premixing of propylene with ammonia is particularly important because that The occurrence of explosive mixtures is much greater here than in the case of methane. The explosion range of propylene-air mixtures is between 2.0 and 11.1 percent by volume. In the case of propane, this range is somewhat smaller at 2.37 to 9.5%. Through the Adding about the same volume of ammonia to propylene or propane lowers the upper explosion limit by about 6 to 7%.

509 538/388

The method is explained in more detail using the examples.

example 1

100 m ^{s of} ammonia are intimately mixed with 109 m ^{3 of} methane every hour in a column filled with Raschig rings and at the same time cleaned of any dust particles. This mixture is added in a pipe tangentially 350 m ^s cleaned air is added, the tube being provided at a suitable point with an explosion disc. To the resulting mixture of 559 m ³ , with a methane content of 19.8%, 338 m ^{3 of} air preheated to 200 ° C is added tangentially through several nozzles and passed at a flow rate of about 120 cm / sec (based on at room temperature) through the platinum-rhodium nets clamped in a known manner. The operating time of the nets could be increased by 60% with this method of operation compared to adding all the air at one point .

Example 2

100 m ^{8 of} ammonia are intimately mixed with 95 m ^{s of} propylene and mixed with 240 m ^{3 of} air. 80 m ^{3 of} water vapor and the rest of the air (360 m ³ ), optionally preheated to about 120 ° C., are then added to the actual reactor. After the reaction of the mixture obtained over a known catalyst, e.g. B. cerium phosphate, the reaction mixture is worked up in a manner known per se and the acrylonitrile produced is obtained therefrom. An increased service life of the catalyst was also observed in this experiment.

Claims (3)

Patent claims: 1. Process for the production of hydrocyanic acid and nitriles by catalytic partial oxidation a mixture of lower hydrocarbons and ammonia, characterized in that, that the hydrocarbons are intimately mixed with ammonia and the mixture thus formed, the oxidizing gas, in particular Air, is added in two or more stages. 2. The method according to claim 1, characterized in that the entire oxidizing Gas or only the partial flow supplied in one stage is preheated. 3. The method according to claims 1 and 2, characterized by the addition of water vapor.