Abstract: A process for preparing aromatic amines by hydrogenation of nitroaromatics in the presence of catalysts, forming a fluid, amine-comprising reaction mixture in a reactor, wherein chromatographic analysis of the reaction mixture is carried out to determine the concentration of nitro and nitroso compounds in the reaction mixture.

Abstract: The present invention relates to a continuous process for preparing at least one aromatic amine by hydrogenation of at least one nitroaromatic by means of hydrogen, where a liquid phase comprising at least the aromatic amine and a gas phase comprising at least hydrogen are present, in the presence of a catalyst suspended in the liquid phase at a temperature of from 50 to 250° C. and a pressure of from 5 to 50 bar, wherein the pressure in the reactor is kept essentially constant by continuous adaptation of the amount of hydrogen fed to the reactor, the total amount of hydrogen fed to the reactor is monitored and the introduction of the at least one nitroaromatic is interrupted if the hydrogen uptake in the reactor is not at least 50 mol % of the amount of hydrogen required for stoichiometric reaction of the at least one nitroaromatic to form the at least one aromatic amine.

Abstract: Precipitations of nitrohydroxyaromatic salts out of the nitrated crude products obtained in the nitration of aromatic compounds after alkaline scrubbing, for example mononitrotoluenes, are prevented by contacting the nitrated crude products with an acidic ion exchanger. The nitrated crude products are preferably selected from a feedstream to a distillation column, a bottoms circulation stream of a distillation column and a feedstream to a vaporizer.

Abstract: The invention relates to a process for the continuous preparation of toluenediamine by liquid-phase hydrogenation of dinitrotoluene by means of hydrogen in the presence of a suspended, nickel-comprising catalyst in a reactor with a product isolation unit downstream of the reactor to give a product output from the reactor comprising a liquid phase comprising toluenediamine and dinitrotoluene, in which the nickel-comprising catalyst is suspended, wherein the concentration of dinitrotoluene in the liquid phase of the product output from the reactor in the region between the reactor and the downstream product isolation unit is set to a value in the range from 1 to 200 ppm by weight, based on the total weight of the liquid phase of the product output from the reactor.

Abstract: The present invention relates to a continuous process for preparing at least one aromatic amine by hydrogenation of at least one nitroaromatic by means of hydrogen, where a liquid phase comprising at least the aromatic amine and a gas phase comprising at least hydrogen are present, in the presence of a catalyst suspended in the liquid phase at a temperature of from 50 to 250° C. and a pressure of from 5 to 50 bar, wherein the pressure in the reactor is kept essentially constant by continuous adaptation of the amount of hydrogen fed to the reactor, the total amount of hydrogen fed to the reactor is monitored and the introduction of the at least one nitroaromatic is interrupted if the hydrogen uptake in the reactor is not at least 50 mol % of the amount of hydrogen required for stoichiometric reaction of the at least one nitroaromatic to form the at least one aromatic amine.

Abstract: A process for preparing aromatic amines by hydrogenation of nitroaromatics in the presence of catalysts, forming a fluid, amine-comprising reaction mixture in a reactor, wherein chromatographic analysis of the reaction mixture is carried out to determine the concentration of nitro and nitroso compounds in the reaction mixture.

Abstract: Precipitations of nitrohydroxyaromatic salts out of the nitrated crude products obtained in the nitration of aromatic compounds after alkaline scrubbing, for example mononitrotoluenes, are prevented by contacting the nitrated crude products with an acidic ion exchanger. The nitrated crude products are preferably selected from a feedstream to a distillation column, a bottoms circulation stream of a distillation column and a feedstream to a vaporizer.

Abstract: The invention relates to a process for the continuous preparation of toluenediamine by liquid-phase hydrogenation of dinitrotoluene by means of hydrogen in the presence of a suspended, nickel-comprising catalyst in a reactor with a product isolation unit downstream of the reactor to give a product output from the reactor comprising a liquid phase comprising toluenediamine and dinitrotoluene, in which the nickel-comprising catalyst is suspended, wherein the concentration of dinitrotoluene in the liquid phase of the product output from the reactor in the region between the reactor and the downstream product isolation unit is set to a value in the range from 1 to 200 ppm by weight, based on the total weight of the liquid phase of the product output from the reactor.

Abstract: The invention relates to a process for the electrochemical treatment of aromatic nitro compounds, which comprises the steps: introducing an aqueous composition comprising at least one aromatic nitro compound into the anode space of an electrolysis cell and carrying out an electrolysis at an anodic current density in the range from 0.1 to 10 kA/m2 and a cell potential in the range from 4 to 15 V.

Abstract: The present invention relates to methyl transfer enzymes involved in alkaloid biosynthesis in opium poppy. More particularly, the invention relates to proteins having (R,S)-reticuline 7-O-methyltransferase activity, to proteins having (R,S)-norcoclaurine 6-O-methyltransferase activity and to derivatives and analogues of these proteins. The invention also relates to nucleic acid molecules encoding the proteins, and their derivatives and analogues, and to their use in the production of methylated catechols and tetrahydrobenzylisoquinolines.

Abstract: The present invention relates to methyl transfer enzymes involved in alkaloid biosynthesis in opium poppy. More particularly, the invention relates to proteins having (R,S)-reticuline 7-O-methyltransferase activity, to proteins having (R,S)-norcoclaurine 6-O-methyltransferase activity and to derivatives and analogues of these proteins. The invention also relates to nucleic acid molecules encoding the proteins, and their derivatives and analogues, and to their use in the production of methylated catechols and tetrahydrobenzylisoquinolines.

Abstract: The present invention relates to methyl transfer enzymes involved in alkaloid biosynthesis in opium poppy. More particularly, the invention relates to proteins having (R,S)-reticuline 7-O-methyltransferase activity, to proteins having (R,S)-norcoclaurine 6-O-methyltransferase activity and to derivatives and analogues of these proteins. The invention also relates to nucleic acid molecules encoding the proteins, and their derivatives and analogues, and to their use in the production of methylated catechols and tetrahydrobenzylisoquinolines.