Abstract: A process for synthesis of dimethyl ether is proposed, in which a feed gas mixture (E) containing carbon dioxide and/or carbon monoxide and hydrogen is guided through reaction tubes (1) of a cooled shell and tube reactor (10) that are equipped with a first catalyst and a second catalyst, in which the carbon dioxide present in the feed gas mixture (E) and/or the carbon monoxide present in the feed gas mixture is at least partly reacted over the first catalyst with the hydrogen present in the feed gas mixture to give methanol, and in which, in the same shell and tube reactor (10), the methanol is at least partly converted over the second catalyst to dimethyl ether.

Abstract: A process for preparing an aromatic polyamine mixture including 4,4?-methylenedi(phenylamine) and higher homologues of MDA is provided. The process includes steps of (i) reaction of aniline with formaldehyde by means of an acid catalyst to form a crude product mixture (I), (ii) neutralization of the crude product mixture (I) and removal of the salts formed; (iii) isolation of aniline; (iv) distillation of the resulting crude product mixture so as to separate off (iv-1) a mixture (II) of MDA isomers (II-1) containing from 8 to 20% by weight of 4,4?-methylenedi(phenylamine) and not more than 0.3% by weight of secondary components (II-2) and (iv-2) a low boiler mixture of at least 55% by weight of secondary components (II-2) and MDA isomers (II-1); and (v) recirculation of the mixture (II).

Abstract: The present invention relates to a process for hydrogenating a mixture (G1) in the presence of a catalyst, where the mixture (G1) comprises at least one colorless amine and at least one color-imparting component. As a result of the hydrogenation step, the at least one color-imparting component is firstly partially, preferably fully, hydrogenated, while the colorless amine, in particular aniline, is not hydrogenated or hydrogenated to only a very small extent. The color-imparting components which cause the discoloration of the amine which is itself in principle colorless are thus removed by hydrogenation, as a result of which purification of the colorless amine or the mixture (G1) is achieved.

Abstract: A process for preparing an aromatic polyamine mixture including 4,4?-methylenedi(phenylamine) and higher homologues of MDA is provided. The process includes steps of (i) reaction of aniline with formaldehyde by means of an acid catalyst to form a crude product mixture (I), (ii) neutralization of the crude product mixture (I) and removal of the salts formed; (iii) isolation of aniline; (iv) distillation of the resulting crude product mixture so as to separate off (iv-1) a mixture (II) of MDA isomers (II-1) containing from 8 to 20% by weight of 4,4?-methylenedi(phenylamine) and not more than 0.3% by weight of secondary components (II-2) and (iv-2) a low boiler mixture of at least 55% by weight of secondary components (II-2) and MDA isomers (II-1); and (v) recirculation of the mixture (II).

Abstract: The present invention relates to a process for hydrogenating a mixture (G1) in the presence of a catalyst, where the mixture (G1) comprises at least one colorless amine and at least one color-imparting component. As a result of the hydrogenation step, the at least one color-imparting component is firstly partially, preferably fully, hydrogenated, while the colorless amine, in particular aniline, is not hydrogenated or hydrogenated to only a very small extent. The color-imparting components which cause the discoloration of the amine which is itself in principle colorless are thus removed by hydrogenation, as a result of which purification of the colorless amine or the mixture (G1) is achieved.