Abstract: A process is described for obtaining pure isocyanate isomers from a mixture of isocyanate isomers by suspension crystallization and the isolation of isomerically pure crystals, which is characterized in that, prior to the isolation of the crystals, 5 to 40% by weight of the crystals produced are remelted while simultaneously increasing the temperature of the crystal slurry by 4.5 to 9° C.

Abstract: A process is provided for the purification of sulfuric acid contaminated with impurities, such as nitric acid, nitrosylsulfuric acid, dinitrotoluenes and mononitrotoluenes, wherein this contaminated sulfuric acid was obtained from the production of nitrated toluene using toluene and nitric acid. The contaminated sulfuric acid is preheated to a temperature in the range of 50 to 180.degree. C. in a heat exchanger. The heated, contaminated sulfuric acid is freed from steam-volatile impurities, such as dinitrotoluenes and mononitrotoluenes, and the nitrogen-containing compounds within the sulfuric acid are decomposed by counter currently contacting the contaminated sulfuric acid with steam and vapors from a downstream concentration step in a steam stripper, which is operated at a pressure ranging from 300 to 1,000 mbars. The steam-stripped sulfuric acid is fed into a first concentration stage, which is operated at the same pressure used in the steam stripper.

Abstract: The present invention is directed to a process for simultaneously obtaining pure carbon monoxide and pure hydrogen in a steam reformer plant for hydrogen or ammonia generation, having a primary reformer, a secondary reformer and downstream thereof, a CO conversion stage. A part gas stream of the synthesis gas stream, which is discharged from the secondary reformer having a CO content of between 2 and 20 mol. % and is at a temperature of from 200 to 500.degree. C. and a pressure between 15 and 50 bar, is removed between the secondary reformer and the CO conversion stage. The part gas stream is then is cooled to a temperature below 100.degree. C., thereby condensing out the major part of the steam contained in the gas stream. The remaining raw synthesis gas stream is then guided by way of a multistage gas separation plant in which the gas components H.sub.2, residual steam, CH.sub.4, CO.sub.2 and optionally N.sub.2 are separated, either individually or together, from the CO.

Abstract: The viscosity of a fluid liquid substance is first increased in a multiphase coil in the presence of a gas phase flowing at high speed and then, with separation of the gas phase, the substance is applied to a stirred bed consisting of a solid granular material where it is converted into a solid substance.

Abstract: A process and a device are described for separating a solid residue, after separation, from a solution of the residue in evaporable materials and/or solvents with the addition of up to 20% by weight of high-boiling hydrocarbons that are inert under evaporation conditions of the evaporable materials, heating the mixture to evaporation temperature under vacuum, whereby the evaporable materials evaporate, are drawn off and condensed, and the residue is obtained as a free-flowing solid, the residue solution being introduced onto a stirred bed of granular solid material kept at the evaporation temperature.

Abstract: Aromatic diamines and polyamines are produced by a continuous process for the catalytic hydrogenation of the corresponding dinitro and polynitro compounds at elevated temperature. Heat removed from the reaction mixture may be used to produce steam with an overpressure of .gtoreq.2 bar.

Abstract: A process for the preparation and purification of nitroaromatics by nitration of the corresponding aromatics and subsequent melt crystallization. The residual melts which occur are recycled.

Abstract: In a multiphase flow tube for drying pumpable suspensions to form solids having low residual moisture contents, the process uses brief increases in the pressure of the gas stream to prevent blockages.

Abstract: Viscous copper-containing catalyst waste is split up into solid particles and gaseous dichlorobutene along a steadily curved flow path, the liquid film flowing along an inner tube wall being driven along by the gas flowing at a higher rate in the core.

Abstract: Improved working up of the waste from an isomerization reaction of dichlorobutene by precipitating the copper catalyst used in said process by adding a polar solvent and removing the resulting precipitate by filtration.