Abstract: This invention relates to a process for the purification of acrylic acid from a mixture containing acrylic acid and acetic acid, comprising the following steps: extraction of the mixture containing acrylic acid and acetic acid with an extractant stream, whereby a raffinate stream and an extract stream are obtained, distillation of the extract stream, whereby an acrylic acid stream and a return stream are obtained, wherein the return stream contains acetic acid and is recirculated into the extraction. Furthermore, the invention may include a plant for carrying out this process.

Abstract: A process for producing short-chain olefins by conversion of oxygenates in a multi-stage fixed-bed reactor, in which the individual stages for reaction zones are covered with beds of a granular, form-selective zeolite catalyst and the feed mixture containing oxygenates is added distributed over the reaction stages. An increase of the availability of the fixed-bed reactor for the olefin production with the same or an increased yield of short-chain olefins is achieved in that one or more reaction zones are charged with a distinctly reduced mass flow of the feed mixture containing oxygenates, wherein the reduced mass flow fraction is distributed over other reaction zones.

Abstract: A process for producing olefins from oxygenates includes the following steps: (i) heterogeneously catalyzed conversion of at least one oxygenate to a stream containing propylene, aromatics and cyclic olefins, (ii) at least partial hydrogenation of the aromatics and cyclic olefins to naphthenes, and (iii) at least partial recirculation of the naphthenes into the heterogeneously catalyzed conversion.

Abstract: A process for producing olefins from oxygenates can include the following steps: (i) heterogeneously catalyzed conversion of at least one oxygenate to a product stream containing C2 olefins, C3 olefins, C4 olefins, C5/6 hydrocarbon compounds, and C7+ hydrocarbon compounds; and (ii) separation of a propylene stream consisting of C3 olefins for at least 95 wt-%, wherein at least 10 wt-% of the propylene stream are recirculated into process step (i).

Abstract: A process for producing olefins from oxygenates comprises the following steps: (i) heterogeneously catalyzed conversion of at least one oxygenate to an entire stream containing propylene, aromatics and cyclic olefins; (ii) olefin interconversion of at least a part of the entire stream; (iii) separation of a stream rich in aromatics from the reaction product of the olefin interconversion; and (iv) hydrogenation of the stream rich in aromatics.

Abstract: A distillation column with external circulation evaporator and a sedimentation zone in the bottom of the column, from which the evaporator circulation is fed, and use of the distillation column for the distillation of acrylic acid.

Abstract: A process for producing short-chain olefins by conversion of oxygenates in a multi-stage fixed-bed reactor, in which the individual stages for reaction zones are covered with beds of a granular, form-selective zeolite catalyst and the feed mixture containing oxygenates is added distributed over the reaction stages. An increase of the availability of the fixed-bed reactor for the olefin production with the same or an increased yield of short-chain olefins is achieved in that one or more reaction zones are charged with a distinctly reduced mass flow of the feed mixture containing oxygenates, wherein the reduced mass flow fraction is distributed over other reaction zones.

Abstract: A gas scrubber, equipped with heat exchanger surfaces constructed of thermoplates, suitable for cooling and cleaning a hot gas by avoiding an excessive thermal load of the washing liquid.

Abstract: A distillation column with external circulation evaporator and a sedimentation zone in the bottom of the column, from which the evaporator circulation is fed, and use of the distillation column according to the invention for the distillation of acrylic acid.

Abstract: A tubular reactor for carrying out a catalytically supported, homogeneous chemical reaction in the gas phase at an elevated temperature and a subsequent cooling, wherein the reactor is arranged upright, and therefore the tubes extend vertically and the as flows downward through the tubes. The tubes are filled with a catalyst bed in the upper part thereof extending in the reaction zone of the reactor and are filled with a structured packing in the lower part, the cooling zone of the reactor.

Abstract: For the distillation of temperature-sensitive liquids, in particular acrylic acid and its esters, the liquid is heated in a column and at least partly evaporated. The vapor is guided through a condenser provided inside the column, in which the vapor is at least partly condensed. The condensed liquid is at least partly withdrawn from the column. The distillation is characterized in that the vapor not condensed yet is guided through the condenser cocurrently to the condensed liquid.

Abstract: An apparatus for discharging bulk material from a container containing gas includes a single-shaft screw conveyor including a conveying tube having an axis of symmetry. A purge tank is disposed downstream of the screw conveyor with the conveying tube opening into the purge tank. The purge tank includes ports for a supply and discharge of a purge gas stream and an outlet opening for the bulk material. A closing cone with a cone tip and an axis of symmetry is shiftably mounted on its axis of symmetry. The closing cone is pressed with the cone tip from outside into an outlet opening of the conveying tube. The axis of symmetry of the closing cone coincides with the axis of symmetry of the conveying tube.

Abstract: A process for the continuous production of melamine from urea by means of a fluidized-bed reactor, wherein process gas guided in the process circuit is used as fluidizing gas and wherein the temperature of the process gas at the inlet of the conveying means for the fluidizing gas is adjusted by adjusting the mixing ratio of a process gas stream guided over a scrubber and of a process gas stream guided past the scrubber.

Abstract: In a process for distilling polymerization-prone compounds from liquid mixtures of matter which, apart from the readily polymerizable compound, also contain other components and also polymerization inhibitors, the evaporator is operated in forced circulation and at a pressure which makes possible superheating of the liquid with respect to its boiling point at the pressure within the distillation column. This is achieved by transporting the superheated liquid against a flow restrictor, e.g. an orifice plate. The liquid which is expanded and partially evaporated on passage through the flow restrictor is returned to the distillation column. In this manner the formation of an open vapour space in the evaporator circuit after heating downstream of the heat exchanger is avoided in that, in the design of the evaporator of the prior art, formation of polymer deposits frequently occurs.

Abstract: A gas scrubber, equipped with heat exchanger surfaces constructed of thermoplates, suitable for cooling and cleaning a hot gas by avoiding an excessive thermal load of the washing liquid.

Abstract: A process for the continuous production of melamine from urea by means of a fluidized-bed reactor, wherein process gas guided in the process circuit is used as fluidizing gas and wherein the temperature of the process gas at the inlet of the conveying means for the fluidizing gas is adjusted by adjusting the mixing ratio of a process gas stream guided over a scrubber and of a process gas stream guided past the scrubber.