CZ340691A3 - process of purifying ammonia gas being a waste when preparing diphenyl amine - Google Patents

Abstract

On gaseous ammonia containing to 1 weight percent of aniline and to 10 weight percent of water is at first countercurrently acted by an ammonia liquor making by its cooling at a temperature lower than 10 degrees of Celsius, and thus treated gaseous ammonia is brought into contact with an activated carbon. Concerning water content variability in the treated ammonia there is effective to adjust the weight ratio of the ammonia liquoir and the aniline present in the ammonia at a value of from 10 to 50 by water addition to the ammonia liquoir.

Description

The present invention relates to a process for purifying ammonia resulting from the production of diphenylamine, which is known as an intermediate for the production of additives for polymers.

BACKGROUND OF THE INVENTION

Diphenylamine is produced on an industrial scale by pressure condensation of aniline in the presence of a catalyst used as an aqueous solution or an aniline soluble complex / at 300-450 ° C (CS 173 389) · Methods for preparing diphenylamine in the gas phase and using catalysts are also known such as alumina in a fixed bed · ammonia dropped from the process is saturated with aniline and also contains some, varying amounts of water · Aniline, as a valuable chemical raw material, is isolated from the ammonia drop off and its efficacy · However, the efficacy of this proees is limited and this resulting ammonia still contains significant amounts of aniline, depending on the degree of cooling, often in forms of aerosol. · Soiled ammonia is practically impossible to use in chemical processes either for aniline interference or for its undesirable presence * in the final product. odstr · Due to the fact that no simple and economical way of perfect purification of gaseous ammonia from aniline residues has been developed so far, ammonia resulting from the production of diphenylamine has been very limited. · The invention has provided a simple, cost-effective and energy-efficient and environmentally-friendly method of purifying ammonia from the diphenylamine production, which enables its full usable as raw materials in the chemical industry ·

2. SUMMARY OF THE INVENTION

Surprisingly, the extensive experimental study of separation equilibria applied in countercurrent interaction of ammonia water, ammonia gas and aniline has now surprisingly found that ammonia from the diphenylamine production can be almost completely freed of aniline, without the need for extremely refrigerated, according to the invention.

The principle of the invention consists in that up to 1% by weight of aniline and up to 10% by weight of water are initially countercurrent with ammonia water per ammonia gas and the treated ammonia gas is contacted with activated carbon. Ammonia water can be achieved, for example, in a packed column, in a packed-bed column, or in a tray column.

Perfect contact of the treated ammonia gas with activated carbon is achieved, for example, in a fixed bed adsorber with a granular activated carbon charge. At the same time, the charcoal works as an aqueous aerosol particle separator to be entrained with ammonia, so that the resulting ammonia is also free of this form of moisture which could interfere with its batch processing or transport using a compressor for example. It is preferred that the weight ratio in the process of utilizing ammonia water and aniline present in the purified ammonia is adjusted to a value of 10 to 50 by adding water to the ammonia water produced at the exit of the column to a temperature of less than 10 °. C and returning countercurrent to the process · This achieves that the solution formed by deposition of ammonia water on purified ammonia consists of a single-water phase · This greatly reduces the aniline vapor pressure above the solution and proportionally increases the separation efficiency · Addition of water also improves · The amount of water added depends on the water content of the purified ammonia gas and it is not advisable to increase it too much, as this increases the amount of ammonia that is recycled to the diphenylamine process as ammonia water.

In addition to simplicity, investment and energy efficiency, a great advantage of the process according to the invention is the fact that it does not generate any waste since the first stage ammonia water containing aniline as well as the aniline contaminated steam condensate formed in the second stage during regeneration of the active the ammonia resulting from the diphenylamine production, treated according to the process of the invention, is practically devoid of aniline and is suitable both as a raw material and for the production of products such as industrial fertilizers ·

DETAILED DESCRIPTION OF THE INVENTION

Example 1

In the diphenylamine production, the waste ammonia gas containing aniline and water is purified by indirect cooling with water in a condenser to a temperature of 35 ° C and subsequently further indirectly cooled to 0 ° C. Ammonia gas at 0 ° C contained 0.02% aniline and 5% water · Water content far exceeds equilibrium, indicating the presence of aqueous aerosol in ammonia gas * Due to the aniline content stated, the ammonia thus obtained benefit burns · Example 1 illustrates the current known state ·

Example 2

The gaseous ammonia resulting from the production of diphenylamine, at a temperature of 35 ° C, containing 0.9% by weight of aniline and 5.9% by weight of water, was fed to the bottom of a laboratory column of 2.5 cm diameter and 1 m height filled with ceramic rings , equipped with a bad cooler on the head, where the ammonia is discharged, cooled to 0 ° C, and the condensate (ammonia water) flows down the cartridge and is discharged through the siphon. The ammonia gas leaving the column was fed to an adsorber filled with granulated activated carbon at a rate of about 0.1 m @ ^-1 with respect to the cross-section of the absorber. The aniline content of the ammonia was determined by absorbing the ammonia into the water

- 4 formation of ammonia water, which was analyzed and the aniline content found was converted to ammonia gas. · The ammonia water content was determined by its absorption into dry methanol, analysis and conversion to ammonia gas.

These values were found

Sample Aniline content Water content /% by weight · / ——— ammonia fell off production diphenylamine, mp 35 ° 0 0.9% by weight * 7.9 ammonia at the exit of the bad cooler, t at 0 ° C about 50 ppm 0.51 ammonia at the outlet of the adsorber, mp 5 ° C unstable 0, -32

Example 3

Using the apparatus and under the conditions of Example 2, the difference was that 100 cm.h of water was fed to the head of the box:

Sample Aniline content Water content /% by weight * / ammonia fell off from the production of diphenylamine, t »35 ° C ammonia at the outlet of the bad cooler, t »0 ammonia at the outlet of the adsorber, t 5 0 0.85% * about 40 ppm unstable 5.8 0.55 0.35

Lower aniline content at the outlet of the first stage is advantageous because the working cycle of the second stage is prolonged *

The illustrative examples illustrate that the process according to the invention allows the ammonia resulting from the production of diphenylamine to be practically completely deprived of aniline and utilized without any problems in the chemical prlemyl, for example for the production of industrial fertilizers * These examples illustrate but do not limit claims *?

Claims (3)

PATENT CLAIMS 1 A process for purifying ammonia resulting from the production of diphenylamine containing up to 1% by weight of ammonia; % aniline and up to 10 wt. Water, characterized in that ammonia gas is first countercurrently treated with ammonia water and the treated ammonia gas is contacted with activated carbon. 2. The process according to claim 1, wherein the ammonia water is obtained by cooling the waste ammonia gas to below 10 [deg.] C. 3. The process according to claim 1, wherein the weight ratio of ammonia water to aniline present in the waste ammonia is adjusted to a value of 10 to 50 by adding water to the ammonia water.