DE954416C - Process for the production of aminonitriles and diamines - Google Patents

Description

Process used for the production of aminonitriles and diamines one for the hydrogenation of technical dinitriles to aminonitriles or diamines the usual hydrogenation catalysts, the yields and purity of the Products sometimes unsatisfactory, especially when they are used for the manufacture of plastics, z. B. polyamides to serve. As is known, can be used in the hydrogenation Separate undesired by-products formed only with difficulty; a distillation usually does not lead to the goal.

It has now been found that the formation of undesirable by-products can be avoided in the hydrogenation of dinitriles can be kept to a minimum if one is basic active compounds of alkalis, alkaline earths or earths in the catalysts and. neutralized the reaction mixture prior to hydrogenation. Be that way This basically reacting substance, which, as has been found, the reason for its formation give of troublesome by-products, bound. The success of the process consists z. B. is that the adipic acid dinitrile remains free of 2-Cyancyclo pentanonimin, both in itself and in the form of its hydrogenation product only imperfectly and is extremely difficult to separate from the hexamethylenediamine.

As basic impurities in the catalysts or often in them The carrier substances used are mainly the oxides and hydroxides of alkalis Called alkaline earths and alkaline earths. These impurities still come from the manufacture of the catalysts or their Carriers. For example Raney catalysts often contain detectable amounts of aluminum or alkali. The catalyst supports, e.g. B.

Silica gel, contain mostly more or less considerable Quantities of alkali, alkaline earth or alkaline earths. Catalysts with only small ones Amounts of such alkaline compounds can e.g. B. in the hydrogenation of adipic dinitrile, the formation of up to about 20% high-boiling or undistillable residues cause.

As acids to neutralize alkaline compounds inorganic or organic acids such as phosphoric acid, sulfuric acid, acetic acid, Succinic acid, or adipic acid, are used. The catalysts are either with a aqueous solution of the acids mentioned washed out or impregnated. Organic acids can also advantageously be added directly to the dinitrile to be hydrogenated. A small excess of the acid is not harmful to the hydrogenation. Through the pre-treatment according to the invention, complete or partial hydrogenation is obtained the dinitrile yields of 95% and more of diamine or aminonitrile of a purity which meets all technical requirements.

The ones in the examples below. specified parts are parts by weight.

Example I An iron-cobalt catalyst applied to strands of silica, the 0.8% basic constituents from the manufacture of the silica strands contains, is soaked with an aqueous phosphoric acid solution so that its content of free phosphoric acid is 0.3%. After the usual drying and reduction the catalyst for the hydrogenation of 250 parts of adipinic acid dinitrile in 250 Share related toluene. The hydrogenation is carried out at an initial hydrogen pressure of 600 and 300 atm carried out. After 6 hours, the pressure remains constant and with it the hydrogen uptake completed. The pressure is released and the clear, colorless solution is separated off from the catalyst. After evaporation of the solvent, 256 parts of a are obtained by distillation Mixture consisting of e-aminocapronitrile and hexamethylenediamine in a ratio 6.3: I. A residue of 3.20 / 0, based on the adipic dinitrile used. When working under the same conditions, but without phosphoric acid treatment of the catalyst, a distillation residue is obtained from I8, 60 / o.

Example 2 A 17% cobalt applied to strands of silica and hydrogenation catalyst containing 0.25% phosphoric acid is introduced into a high pressure tube with a clear width of 30 mm and a height of 21/2 m.

At 850 and 300 at initial hydrogen pressure, 300 parts per hour a mixture of adipic dinitrile and toluene in a ratio of 1: 1 and 0.05 0 / o adipic acid (based on the dinitrile-toluene mixture) was added. The reaction product (300 parts) results in the distillation after removal of the solvent I, 20 / o First run, 96.4% hexamethylenediamine with a melting point of 40.6 ° and 1.6% residue.

Example 3 300 parts of a mixture of succinic acid dinitrile and Toluene in a ratio of 1: 1 are added every hour in the device described in Example 2 at 850 and 300 at initial hydrogen pressure with the catalyst described in Example 2, containing 0.50 / 0 phosphoric acid, treated. 300 parts of hydrogenation product are obtained that in the distillation 3.20 / o first run, 91.70 / 0 tetramethylenediamine and 4.40 / 0 Residue results.

Claims (3)

P A T E N T A N S P R Ü C H E: I. Process for the production of Amine nitriles and diamines by catalytic hydrogenation of dinitriles, thereby characterized in that one has a basic verb, in dungen the alkalis, alkaline earths or earths in the catalysts and the reaction mixture are neutralized before the hydrogenation. 2. The method according to claim I, characterized in that catalysts used previously with appropriate. Quantities of acids have been treated. 3. The method according to claim 1 and 2, characterized in that one adding appropriate amounts of, in particular, organic acids to the reaction mixture. References considered: J. Gen. Chem. 12 (1942), 518 off.; Chemical AS stracts 37: 27I6 (1943).