Abstract: A process for the continuous recovery of (meth)acrylic acid from the reaction gas of a catalytic gas-phase oxidation comprising the following process stages is proposed: I quenching of the reaction gas by evaporative cooling using a high-boiling solvent, II separation of the (meth)acrylic acid from the quenched reaction gas by absorption into the high-boiling solvent, III separation of the solvent laden with (meth)acrylic acid by rectification into a first part-stream IIIA), which contains predominantly (meth)acrylic acid, and into a second part-stream IIIB) which contains predominantly the solvent, IV recycling of the stream IIIB) to process stage II and V distillative production of (meth)acrylic acid from stream IIIA), all liquid residual streams obtained in process stage V being recycled to process stage I.

Abstract: A process for the fractional condensation of a hot gas mixture which as well as acrylic acid contains at least one further condensable component in a column in the presence of at least one stabilizer comprises metering in at least a portion of the at least one stabilizer as a melt.

Abstract: A process for inhibiting polymerization in the preparation of (meth)acrylic esters of C1–C8-alcohols, wherein the pH of the water of reaction supplied to the C1–C8-alcohol recovery is greater than 7.

Abstract: In order to further develop a microcontroller (100) the programming of which is carried out in at least one machine-dependent assembler language in which the assembler commands, with the exception of conditional program jumps or branches, can be executed in essence independently of data, together with a method for processing the programming of the microcontroller (100) carried out in at least one machine-dependent assembler language, in such a way that the program running on the microcontroller (100) is entirely secret and unpredictable, i.e. is not reproducible, for an external observer, it is proposed that the program jumps or branches are executed—in dependence on the state of at least one random number generator (10) and/or—independently of the internal state of the programming of the microcontroller (100).

Abstract: The invention relates to a process for preparing optically active 5-hydroxy-3-ketoesters of formula A1 or A2, or one of the tautomers thereof, the use thereof for preparing optically active dihydropyrones of formula B, and the use of the dihydropyrones of formula B thus prepared as starting compounds for preparing pharmaceutically active compounds, particularly Tipranavir.

Abstract: Higher (meth)acrylates IV are prepared by transesterification of a lower (meth)acrylate I with a higher alcohol R2OH in the presence of a stabilizer or stabilizer mixture and of a catalyst or catalyst mixture, by a process in which the liberated lower alkanol R1OH is separated off and is fed at least partly to the preparation of the lower (meth)acrylate I.

Abstract: Organic compounds are prepared by heterogeneously catalyzed partial gas-phase oxidation of precursor compounds by a process in which a portion of the reaction gas starting mixture is brought from a low initial pressure to a higher final pressure by means of a radial compressor.

Abstract: In a process for preparing acrylic acid, an acrylic acid-containing product gas mixture obtained by catalytic gas phase partial oxidation of a C3 precursor of acrylic acid, after direct cooling with a quench liquid, is fractionally condensed in a separating column provided with internals, rising into itself with sidestream takeoff of crude acrylic acid, and the acrylic acid oligomers which form are dissociated and the resulting dissociation gas is subjected to a countercurrent rectification before it is recycled.

Abstract: In process for cleaning tray columns which are used for the purposes of rectifiying liquids comprising (meth)acrylic compounds, a basic liquid is conveyed downward through the tray column and a gas is passed through the column in countercurrent to the basic liquid at an average gas phase differential pressure over all trays of at least 0.5 mbar/tray.

Abstract: The present invention describes a process for preparing (meth)acrylic esters by acid-catalyzed esterification of (meth)acrylic acid or by transesterification of (meth)acrylic esters with alcohols, by adding the (meth)acrylic acid or the (meth)acrylic ester at a metering rate of less than 250 g per hour and liter of reactor volume and/or using at least 0.2 mmol of polymerization inhibitor per kg of alcohol and per meq/kg of peroxid number of the alcohol determined by the Sully method and/or thermally treating the alcohol in the absence of water before the esterification or transesterification.

Abstract: A thermal separating process for removing a stream containing enriched (meth)acrylic monomers from a mixture containing (meth)acrylic monomers, in which the liquid phases retained in the separating space at high temperature and high (meth)acrylic monomer content are minimized.

Abstract: In a process for preparing an ester of an unsaturated carboxylic acid by reacting an ester of the unsaturated carboxylic acid and a C1-C4-alkanol with an alcohol R3OH, where R3 is a C4-C20-alkyl radical, a C5-C7-cycloalkyl radical, a phenyl-C1-C4-alkyl radical or a C2-C12-alkyl radical substituted by at least one NR5R5 group or by from 1 to 3 hydroxyl groups or C1-C4-alkoxyl groups or interrupted by one or more oxygen atoms, where the radicals R5 are, independently of one another, C1-C6-alkyl or together with the nitrogen atom form a 5- to 7-membered heterocyclic ring which may contain a further nitrogen or oxygen atom, in the presence of a transesterification catalyst, the transesterification catalyst used is at least one metal alkanolate containing at least one OR1 group, where R1 is a 2,2,6,6-tetraalkyl-1-oxylpiperidin-4-yl radical.

Abstract: Mixtures containing monomers having at least one ethylenically unsaturated group are chemically and/or physically treated in the presence of the reaction products of alkylsuccinic anhydrides and stable N-oxyl radicals having a hydroxyl group.

Abstract: The invention relates to a method for producing (meth)acrylic acid esters by transesterification of the (meth)acrylic acid with a higher alkanol in the presence of an acid catalyst, at least one polymerization inhibitor and one organic solvent that forms an azeotropic mixture with water. The reaction mixture is heated to the boiling point of the mixture in a reactor that comprises a distillation unit with a column and a condenser. The content of the reactor is recirculated via an external evaporator and heated to the boiling point, and the azeotropic mixture is distilled off. The organic solvent forms a reflux and at least a part of the solvent reflux is recirculated between the reactor and the evaporator. The inventive method allows for the production of higher (meth)acrylic acid esters in a reactor with a circulation evaporator without using copper salts as the polymerization inhibitors.

Abstract: Polymerizable compounds are prepared and/or worked up using at least one liquid ring pump by a process in which a working liquid which contains a material stream from the preparation and/or working-up of the polymerizable compound is used in a liquid ring pump.

Abstract: The invention relates to a process for preparing optically active 5-hydroxy-3-ketoesters of formula A1 or A2, 1

Abstract: An inhibitor mixture containing, as components, a) at least one nitroxyl radical (derivative), b) at least one phenol (derivative) and c) at least one chemical compound which contains at least one phosphorus atom which has the oxidation state +3 is preferably used for stabilizing compounds capable of free radical polymerization.

Abstract: A process for preparing acrylic acid and/or acrylates which comprises the following stage A and, if desired, B and C: A: cooling a gaseous reaction mixture which comprises acrylic acid and is obtained in the gas-phase oxidation to prepare acrylic acid, using oligomeric acrylic acid or a mixture of acrylic acid and oligomeric acrylic acid, to give a gaseous mixture comprising acrylic acid and a quench bottom product which comprises oligomeric acrylic acid; B: separating the gaseous mixture comprising acrylic acid, to give a low-boiling fraction, a crude acrylic acid, and a bottom product, which comprises oligomeric acrylic acid; C: esterifying the crude acrylic acid obtained in stage B by means of one or more alkanols.

Abstract: A water lance blower for cleaning heat installations is disclosed. A water lance linked with a water feed conduit system is swivel-mounted with its orifice disposed in a hatch. The water lance can blow a jet of water through the heating installation in operation and through which flames and/or flue gases are guided to wall areas that can be reached from the hatch. The water lance blower is provided with a drive system with at least two drive units that control the water lance, and with a holding device that fastens the water lance blower onto the heating installation. Further, parts of the water feed conduit system are integrated onto the holding device, thereby substantially limiting the size of the water lance blower to the swivel range of the water lance.

Abstract: In a process for the fractional condensation of an acrylic acid-containing product gas mixture of a gas-phase partial oxidation of C3 precursors of acrylic acid with molecular oxygen under heterogeneous catalysis, the separation column used contains both dual-flow trays and hydraulically sealed cross-flow trays as baffles having separation activity.