Abstract: In a process for mixing reactant streams (1, 2; 5) to produce a product stream (10) using a mixing configuration (15, 16) having a number of reactant feed points, an excess component stream of one reactant is divided into two reactant substreams (1, 2) and fed into the suction region (3, 4) of a mixing space (12) at right angles to a deficient component (5) entering the mixing space (12).

Abstract: Starting material streams are mixed in a mixer (13) for the phosgenation of amines by a process in which the reaction product (3) is removed in a closed loop and the starting material streams (1.2) contain organic solvents. The main streams (1.1, 2.1) and/or part-streams (1.2, 2.2) of the starting materials (1, 2) come into contact with one another according to the countercurrent principle.

Abstract: In a process for preparing mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having a reduced content of chlorinated by-products and a reduced iodine color number by two-stage reaction of the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylenepolyamines with phosgene in the presence of at least one inert organic solvent at elevated temperature, separation of the excess phosgene and solvent after the phosgenation is complete and thermal treatment of the reaction product, the mass ratios of phosgene to hydrogen chloride in the residence time apparatus of the second stage of the phosgenation are at the same time 10-30:1 in the liquid phase and 1-10:1 in the gas phase.

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C.

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.

Abstract: The invention relates to a process for the preparation of amines by hydrogenation of nitro compounds, which comprises carrying out the hydrogenation in a vertical reactor whose length is greater than its diameter, having a downward-facing jet nozzle arranged in the upper region of the reactor through which the starting materials and the reaction mixture are fed in, and having an outlet at any desired point of the reactor, through which the reaction mixture is fed back to the jet nozzle in an external circuit by means of a conveying means, and having flow reversal in the lower region of the reactor.

Abstract: In a process for preparing amines, in which at least one compound containing at least one nitro group is reacted with hydrogen in the presence of a supported catalyst comprising, as catalytically active metal, nickel, if desired together with at least one metal of transition group I, V, VI and/or VIII, the reduced and stabilized supported catalyst comprises nickel crystallites having a bimodal nickel crystallite size distribution having maxima at 30-80 Angstrom and 81-150 Angstrom on a support comprising ZrO.sub.2, ZrO.sub.2 --HfO.sub.2 and/or SiO.sub.2 --ZrO.sub.2 and/or SiO.sub.2 --ZrO.sub.2 --HfO.sub.2 and in the reduced and passivated state has a nickel content of 60-80 percent by mass, an SiO.sub.2 content of 0-20 percent by mass, a ZrO.sub.2 content of 0-40 percent by mass, an HfO.sub.2 content of 0-4 percent by mass and after further reduction for one hour at 100.degree. C. has a degree of reduction of at least 70%.