DE697421C - Process for the production of diphenylamine - Google Patents

Description

Process for the preparation of diphenylamine It has been found that diphenylamine can be prepared in an advantageous manner with high yields if aniline is exposed at elevated temperature to the action of catalysts which are made wholly or partly from unaged aluminum hydroside. Unaged aluminum hydroxide is a water-containing form of clay which, when mixed with water or after treatment with a peptic agent, such as hydrochloric or nitric acid, is a colloidal solution which is less than that required to convert all aluminum into chloride or nitrate is able to form. It can be such from appropriate highly basic aluminum salts, .insbesondere their solutions as well as colloidal, Aluminiumvcrbindungcn containing solutions, produce, and must be noted that a strong alkaline reaction is avoided in Gegemdart non-volatile alkalis. In contrast to this, commercial toric dehydrate, which is known to be produced from sodium aluminate solutions by stirring with clay or precipitating with carbonic acid, i.e. from a strongly alkaline solution in the presence of non-volatile alkalis, is a strongly aged and therefore ineffective, poorly peptisable let aluminum hydroxide produced from which, although useful for many purposes catalysts, but to have a deal for the present Venvendtuigszweck overall effectiveness rings.

To prepare the catalyst, the hydroxide is expediently in lumpy form, by a suitable treatment, preferably by heating, largely dehydrated and so converted into the water-insoluble form. Man the clay can also be deposited on carrier masses or suitable as carriers Soak fabrics with the colloidal aluminum hydroxide solution and then the aluminum hydroxide in the water-insoluble form.

The use of the catalysts. unaged aluminum hydroxide has the advantage, among other things, that it can be used even at relatively low temperatures can achieve good yields and that undesired side reactions or avoided are largely pushed back when using conventional dehydrating agents Catalysts, e.g. B. Bauxite. Bleaching earth, kaolin and the like - for separating coal on the catalyst and, as a result, an early reduction in the catalytic effect to lead. The catalysts can be used in bulk or, as already indicated above, on Carriers are applied. A deposition of carbon on the catalyst takes place here only to a very limited extent; it affects the effectiveness of the catalyst after prolonged use, this can be achieved by heating in the air stream to temperatures which advantageously do not lie above 600 °, are revived, whereby it is its original Regains effectiveness.

The preparation of diphenylamine is expediently carried out in such a way that that one continuously evaporates the aniline, through heat exchange, with already converted Brings products or in a preheater to the reaction temperature and on it in a reaction vessel over one made from non-aged aluminum hydroxide " Catalyst conducts.

The reaction mixture can be in columns connected to the apparatus are continuously broken down into its component parts; dar-, split off ammonia is expediently in water or sulfuric acid, the unchanged aniline absorbed Implementation fed back. The formed Diphenylatnin can if desired by Distillation in vacuo to be further purified.

The yield of diphenylamine is usually 95 to 990% of the converted aniline; the amount of aniline converted increases with increasing temperature and longer residence time. One works mostly at temperatures between 300 and 50 °; the lower the temperature, the greater the use necessary to obtain good yields. Good results can be achieved, for example, when working at temperatures from .12o to .150 '' with throughputs of from 60 to 100 g of aniline per liter of catalyst.

The process can be carried out at ordinary, elevated or reduced pressure be performed. Example About one made from unaged aluminum hydroxide Catalyst are per liter of catalyst per hour under normal pressure : 130` Suction aniline conducted. 450 ö of the aniline passed through is converted into diphenylamine transferred, more than 54 ° 'o remain unchanged and are returned to the reaction space fed. In a yield of over 9So = o_ of theory, calculated on the converted Anilni, about 33 g of diphenylamine are obtained per liter of catalyst per hour.

Substituting hourly only 20g of aniline per liter of catalyst by so already at 32o to 350 "about 35 to 4oo, 'o of the aniline in diphenylamine converted; obtained about 7.- diphenylamine per hour per liter of catalyst in a yield of 95 to 960; o the theory.

The superiority of the process over working with other catalysts can be seen from the following table, in which the percentage conversions of aniline for a single pass through a reaction vessel are given at .130 "'; the amount passed through was in each case .log aniline per liter of catalyst :, Catalytic converter I universal kit 'Bauxite (Vogelsberg) ..... . . . . . . . . . . . 7th Fuller's earth, known by the name Tonsil AC. . . . . . . . . . . . . . . . . . . . 13th Made from aged aluminum hydroxide. . 17th From aged + ro 0; '0 not aged- tem aluminum hydroxide. . . . . . . . . 2o Made from non-aged aluminum hydride oxide ........................... 59

Claims (1)

1 "1NNsi.'tztlCli: Method for of Diplicnylaniin from Aniline at elevated temperature using aluminum oxide catalysts, characterized in that claß one uses such catalysts, which are wholly or partly made of unaged E \ luniinitiniltydro%,) - tl made sied. .