Abstract: The present invention relates to A method for producing aromatic amines by the hydrogenation of aromatic nitro compounds. This method comprises: A) supplying aromatic nitro compounds and hydrogen to a reactor and contacting them with a hydrogenation catalyst; and B) stopping the supply of aromatic nitro compounds and hydrogen to the reactor. In addition, B) is carried out by: B1) stopping the supply of aromatic nitro compounds to the reactor such that any remaining aromatic nitro compounds present in the reactor and/or in parts of the installation that are fluidically connected to the reactor upstream react with the hydrogen that is still being supplied to the reactor, and B2) stopping the supply of hydrogen after a predetermined time interval and/or after the concentration of aromatic nitro compounds in the gas flow entering the reactor falls below a predetermined value.

Abstract: The present invention relates to a method of producing aromatic amines by hydrogenation of aromatic nitro compounds. This method comprises the steps: A) making a reactor containing a hydrogenation catalyst available; B) supplying aromatic nitro compounds and hydrogen to the reactor and contacting them with a hydrogenation catalyst, with at least the hydrogen which is supplied to the reactor is by means of a compressor and the compressor contains an operating fluid which at least partially contacts the hydrogen; and C) regenerating the hydrogenation catalyst by heating and contacting it with oxygen. After step C), steps D1) and/or D2) are carried out. Step D1) removes at least some of any fluids that are present in the reactor and/or in parts of the installation which are fluidically connected to the reactor downstream, with the fluids having been at least partially present in the reactor and/or in these parts of the installation during C).

Abstract: The invention relates to a method for producing nitrobenzene, in which crude nitrobenzene is first produced by nitrating benzene and said crude nitrobenzene is then washed in succession in at least one acid wash, in at least one alkaline wash and in at least one neutral wash, at least one additional wash with an aqueous solution of a potassium salt being interposed between the last alkaline wash and the first neutral wash.

Abstract: The invention relates to a process for the continuous production of nitrobenzene by nitration of benzene with a mixture of nitric acid and sulfuric acid under adiabatic conditions, in which unreacted benzene is separated from the crude product obtained after phase separation before washing thereof, using the adiabatic heat of reaction.

Abstract: The present invention relates to a device for separating two immiscible phases and/or for extracting one phase with another phase (phase separation or extraction device), comprising at least one vessel for receiving the at least two phases, at least one pipe for supplying a fluid to the vessel, at least one pipe for discharging a fluid from the vessel, and at least one arrangement comprising a transparent disk for observing the separation operation or the extraction operation, wherein at least the side of the transparent disk that faces the phases to be separated or extracted consists of sapphire (sapphire glass) or mica ( mica disk), and to the use of such a device in the preparation of di- and polyamines of the diphenylmethane series.

Abstract: In a chemical reactor for heterogeneously catalysed reaction of a fluid, comprising a holding device for catalyst particles and/or inert particles (80, 100) through which the fluid flows, the side of the holding device lying upstream when viewed in the direction of flow of the fluid comprises knitted wire mesh fabric (50), and the average clear mesh width of the knitted wire fabric (50) is smaller than the average particle size x50.3 of the particles (80, 100). The invention furthermore relates to a process for reaction of a fluid, wherein the reaction is carried out in a reactor according to the invention in the presence of heterogeneous catalyst particles (80) and the catalyst particles (80) are arranged in the holding device for catalyst particles (80). The invention also provides the use of knitted wire mesh fabric (50) as a holding device for catalyst particles and/or inert particles (80, 100) in chemical reactors.

Abstract: The present invention relates to a continuous process for the production of nitrobenzene by nitration of benzene with nitric acid or mixtures of nitric acid and sulfuric acid to give a crude nitrobenzene, washing of the crude nitrobenzene by means of at least one of each of an acid, alkaline and neutral washing, there being obtained a pre-purified nitrobenzene which, as well as containing nitrobenzene, at least contains also low boilers, optionally middle boilers as well as high boilers and salts, wherein the pre-purified nitrobenzene is purified further by separating off low boilers in a distillation apparatus by evaporation of the low boilers, and separation of nitrobenzene from the resulting further purified nitrobenzene in a distillation apparatus by partial evaporation of nitrobenzene, wherein pure nitrobenzene is removed from the distillation apparatus in gaseous form and is subsequently condensed, and wherein the non-evaporated portion of the further purified nitrobenzene is fed back into the washing a

Abstract: The invention relates to a process for the continuous production of nitrobenzene by nitration of benzene with a mixture of nitric acid and sulfuric acid under adiabatic conditions, in which unreacted benzene is separated from the crude product obtained after phase separation before washing thereof, using the adiabatic heat of reaction.

Abstract: The present invention relates to a process for restoring the activity of spent catalysts for the hydrogenation of aromatic nitro compounds, in which a regeneration comprising at least a first burning off stage, a first washing stage, a second burning off stage and a second washing stage is carried out at periodic intervals.

Abstract: This invention relates to a process for the continuous preparation of nitrobenzene. This process comprises the adiabatic nitration of benzene with a mixture of sulfuric acid and nitric acid, in which the sum of the concentrations in the reaction zone of the metal ions which form sparingly soluble metal sulfates is less than 900 mg/l, based on the volume of the aqueous phase which contains sulfuric acid.

Abstract: The invention relates to a continuous process for the manufacture of nitrobenzene. This process comprises the nitration of benzene with nitrating acid that contains at least 3.0 wt. % of nitric acid and at least 67.0 wt. % of sulfuric acid, in a reaction space in which the start temperature of the reaction is above 100.0° C. but below 102.0° C. In addition, this process requires that the benzene and the nitrating acid are dispersed in one another several times.

Abstract: The invention relates to a continuous process for the manufacture of nitrobenzene. This process comprises the nitration of benzene with nitrating acid that contains at least 3.0 wt. % of nitric acid and at least 67.0 wt. % of sulfuric acid, in a reaction space in which the start temperature of the reaction is above 100.0° C. but below 102.0° C. In addition, this process requires that the benzene and the nitrating acid are dispersed in one another several times.

Abstract: This invention relates to a process for the continuous preparation of nitrobenzene. This process comprises the adiabatic nitration of benzene with a mixture of sulfuric acid and nitric acid, in which the sum of the concentrations in the reaction zone of the metal ions which form sparingly soluble metal sulfates is less than 900 mg/l, based on the volume of the aqueous phase which contains sulfuric acid.

Abstract: Alkaline waste waters formed in the washing of crude nitrobenzene which has been prepared by the adiabatic nitration of benzene with nitrating acid, washed in an acidic washing process, and then washed in an alkaline washing process are treated. The alkaline waste water being treated generally contains benzene in a concentration of from about 100 to about 3000 ppm and nitrobenzene in a concentration of from about 1000 to about 10,000 ppm. In the process of the present invention, undissolved benzene and/or nitrobenzene are separated from the alkaline waste water, residual benzene and/or nitrobenzene is/are then optionally stripped out of the alkaline waste water, and the alkaline waste water from which benzene and/or nitrobenzene has been removed is heated to a temperature of from 150 to 500° C. under excess pressure with the exclusion of oxygen.

Abstract: Nitrobenzene is produced and then purified using an acidic wash, an alkaline wash, a neutral wash, subjecting a dispersion formed in the neutral wash to electrophoresis to separate water and benzene from the nitrobenzene and recover purified nitrobenzene.

Abstract: Nitrobenzene is produced and then purified using an acidic wash, an alkaline wash, a neutral wash, subjecting a dispersion formed in the neutral wash to electrophoresis to separate water and benzene from the nitrobenzene and recover purified nitrobenzene.

Abstract: Alkaline waste waters formed in the washing of crude nitrobenzene which has been prepared by the adiabatic nitration of benzene with nitrating acid, washed in an acidic washing process, and then washed in an alkaline washing process are treated. The alkaline waste water being treated generally contains benzene in a concentration of from about 100 to about 3000 ppm and nitrobenzene in a concentration of from about 1000 to about 10,000 ppm. In the process of the present invention, undissolved benzene and/or nitrobenzene are separated from the alkaline waste water, residual benzene and/or nitrobenzene is/are then optionally stripped out of the alkaline waste water, and the alkaline waste water from which benzene and/or nitrobenzene has been removed is heated to a temperature of from 150 to 500° C. under excess pressure with the exclusion of oxygen.

Abstract: The present invention relates to polymers that are modified along the polymer chain and are based on conjugated dienes or conjugated dienes and vinyl-aromatic compounds having a content of vinyl-aromatic compounds of up to 60 wt. %, a content of cis-position double bonds of ≧92%, a mean molecular weight of 50,000 to 1,500,000 g/mole and a gel content of ≦5%. The polymers according to the invention can be used for the production of all types of molded articles, wherein in particular their technical and physical properties are improved compared with the prior art.

Abstract: The invention relates to metallized, unsaturated polymer anions stabilized by coordinate bonding and having a high proportion of cis double bonds, to a process for the preparation thereof and also to the use of the new polymer anions for the preparation of graft polymers that can be obtained by reaction of the unsaturated polymer anions with anionically polymerisable, non-polar monomers. From the graft polymers that are prepared in this way the most diverse rubber mouldings can be produced by appropriate vulcanization processes.

Abstract: The invention provides modifiers for the anionic polymerization of conjugated dienes or of conjugated dienes with vinylaromatic compounds, wherein the modifiers are specific aminoethers.