Abstract: Disclosed is an apparatus for recovering an acrylic acid from a mixture containing acrylic acid, acrylic acid dimer and impurities with high boiling point, including: an acrylic acid recovering device that comprises an acrylic acid distillation unit being present within an acrylic acid dimer pyrolysis tank, and is operated under reduced pressure; a separation column for removing impurities with high boiling point from the mixture which is introduced into the acrylic acid recovering device; and a line for introducing the mixture into the acrylic acid recovering device.

Abstract: Disclosed is a shell-and-tube heat exchanger type reactor that can be used for a process of producing unsaturated acids from olefins via fixed-bed catalytic partial oxidation, which comprises at least one reaction tube, each including at least one first-step catalyst layer, in which olefins are oxidized by a first-step catalyst to mainly produce unsaturated aldehydes, and at least two second-step catalyst layers, in which the unsaturated aldehydes are oxidized by a second-step catalyst to produce unsaturated acids, wherein a first catalyst layer of the second-step catalyst layers, disposed right adjacent to the first-step catalyst layer, has an activity corresponding to 5˜30% of the activity of the catalyst layer having a highest activity among the second-step catalyst layers. A method of producing unsaturated acids from olefins by using the reactor is also disclosed.

Abstract: Disclosed is a shell-and-tube heat exchanger type reactor that can be used for a process of producing unsaturated acids from olefins via fixed-bed catalytic partial oxidation, which comprises at least one reaction tube, each including at least one first-step catalyst layer, in which olefins are oxidized by a first-step catalyst to mainly produce unsaturated aldehydes, and at least two second-step catalyst layers, in which the unsaturated aldehydes are oxidized by a second-step catalyst to produce unsaturated acids, wherein a first catalyst layer of the second-step catalyst layers, disposed right adjacent to the first-step catalyst layer, has an activity corresponding to 5˜30% of the activity of the catalyst layer having a highest activity among the second-step catalyst layers. A method of producing unsaturated acids from olefins by using the reactor is also disclosed.

Abstract: Disclosed is a shell-and-tube heat exchanger type reactor that can be used for a process of producing unsaturated acids from olefins via fixed-bed catalytic partial oxidation, which comprises at least one reaction tube, each including at least one first-step catalyst layer, in which olefins are oxidized by a first-step catalyst to mainly produce unsaturated aldehydes, and at least two second-step catalyst layers, in which the unsaturated aldehydes are oxidized by a second-step catalyst to produce unsaturated acids, wherein a first catalyst layer of the second-step catalyst layers, disposed right adjacent to the first-step catalyst layer, has an activity corresponding to 5˜30% of the activity of the catalyst layer having a highest activity among the second-step catalyst layers. A method of producing unsaturated acids from olefins by using the reactor is also disclosed.

Abstract: A shell-and-tube heat exchanger-type reactor including one or more catalytic tubes, each including a first-step reaction zone and a second-step reaction zone, wherein at least one of the first-step reaction zone and the second-step reaction zone is divided into two or more shell spaces by a partition; each of the divided shell spaces is independently heat-controlled; and a heat transfer medium having a temperature from the lowest active temperature of a catalyst layer in a reaction tube corresponding to the first shell space of the first-step reaction zone or the first shell space of the second-step reaction zone to the lowest active temperature of the catalyst layer plus 20° C.; and the first shell space of the first-step reaction zone or the first shell space of the second-step reaction zone is controlled so as to provide a reactant conversion contribution per length of 1.2˜2.5.

Abstract: Disclosed is a simplified apparatus for recovering acrylic acid from a mixture containing acrylic acid, acrylic acid dimer and impurities with high boiling point, in a stable and efficient manner. An apparatus for recovering an acrylic acid from a mixture containing acrylic acid, acrylic acid dimer and impurities with high boiling point, which comprises: an acrylic acid recovering device that comprises an acrylic acid distillation unit being present within an acrylic acid dimer pyrolysis tank, and is operated under reduced pressure; and a line for introducing the mixture into the acrylic acid recovering device, wherein decomposition of the acrylic acid dimer is carried out under reduced pressure at a lower part of the acrylic acid recovering device, while the acrylic acid is recovered by distillation under reduced pressure from a top of the acrylic acid recovering device.

Abstract: Disclosed is a method for producing (meth)acrylic acid comprising a process of recovering (meth)acrylic acid as aqueous (meth)acrylic acid solution from a (meth)acrylic acid-containing gas mixture produced by the catalytic gas phase oxidation of at least one reactant selected from the group consisting of propane, propylene, isobutylene and (meth)acrolein, wherein the recovering process comprises the steps of: (1) feeding the (meth)acrylic acid-containing gas mixture into a quenching tower and condensing it in the quenching tower so as to recover an aqueous (meth)acrylic acid solution from the bottom of the quenching tower, in which some of the recovered aqueous (meth)acrylic acid solution is recycled to the upper portion of the quenching tower so as to condense the (meth)acrylic acid-containing gas mixture; (2) passing the uncondensed part of the (meth)acrylic acid-containing gas mixture from the top of the quenching tower to a distillation tower; and (3) heating the bottom of the distillation tower to separa

Abstract: Disclosed is a simplified method for recovering acrylic acid from a mixture containing acrylic acid, acrylic acid dimer and impurities with high boiling point, in a stable and efficient manner. The method comprises the steps of: introducing the mixture into an acrylic acid recovering device comprising an acrylic distillation unit integrated with an acrylic acid dimer pyrolysis tank; carrying out decomposition of acrylic acid dimmer under reduced pressure and recovering acrylic acid. The method optionally further comprises a step of recycling a portion of the solution obtained from the bottom of the acrylic acid recovering device to the acrylic acid recovering device.

Abstract: Disclosed is a process for producing unsaturated aldehydes and/or unsaturated acids from olefins or alkanes in a fixed bed shell-and-tube heat exchanger-type reactor by catalytic vapor phase oxidation. A heat exchanger-type reactor for use in such a process is also disclosed. The process utilizes at least one first-step reaction zone and a second-step reaction zone that is divided into two or more shell spaces by at least one partition. The process may be applied to a single-step process for producing unsaturated acids from alkanes or alkenes.

Abstract: Disclosed is a temperature measuring device. The temperature measuring device includes: a thermo-well tube; and a cable or wire type temperature measuring means which is installed in a thermo-well tube, wherein temperature measuring means has temperature detecting sensors disposed at an intermediate portion thereof, and the temperature detecting sensors can be moved axially in the thermo-well tube by applying tension to both ends of the cable or wire type temperature measuring means. The present invention also provides a reaction tube in which the temperature measuring device is disposed axially, and a reactor including at least one temperature measuring device or reaction tube as described above.

Abstract: A method of preparing a polycarbonate resin having improved thermal stability is provided. The method includes: mixing polycarbonate having hydroxy terminal groups and a end terminator, a compound of formula (1) (refer to the detailed description section) at normal temperature and pressure to obtain a mixture; and performing a melt reaction on the mixture at 250-320° C. and reduced pressure to highly reduce the final concentration of the hydroxy terminal groups of the polycarbonate resin.

Abstract: A heat exchange-type reactor includes a reaction chamber (1) having mounted therein a plurality of contact tubes (5) filled with a catalyst material; at least one shield plate (11) mounted within the reaction chamber to partition an inner space of the reaction chamber into at least two separate spaces (1d, 1e); a plurality of conduits (13, 15, 17, 19) having entrance (15a, 17a) and exit (13a, 17a) openings through which a heat transfer medium respectively enters and exits, and being mounted to an outer circumference of the reaction chamber (1) corresponding to the partitioned spaces (1d, 1e); and a heat exchange unit connected to the conduits (13, 15, 17, 19) to perform heat exchange of the heat transfer medium, in which the heat exchange unit includes a single heat exchanger that performs the exchange of heat of the heat transfer medium in accordance with the partitioned spaces.

Abstract: The present invention relates to a continuous method for the preparation of an aromatic carbonate by reacting a dialkyl carbonate and an aromatic hydroxy compound in the presence of a heterogeneous catalyst, and a reaction apparatus for the same. The continuous method comprises the step of reacting dialkyl carbonate and an aromatic hydroxy compound in the presence of the heterogeneous catalyst in a loop-type, catalyst-containing reaction apparatus, wherein a reactor equipped with a filter in which the catalyst is contained is connected with a heat exchanger portion for providing necessary heat during the reaction, reaction solution is circulated between the catalyst-containing portion and heat exchanger via a circulation pump, and by-products can be eliminated via a distillation column connected with the reactor.

Abstract: Provided is a method of producing a high-molecular weight modified polycarbonate resin. The method includes a melt condensation polymerization process in which transesterification and quick condensation polymerization are sequentially performed, a spray crystallization process, and a solid state polymerization process. When this method is used, solid state polymerization can be performed without additional drying, milling and fractionation processes so that the operation time and costs are highly reduced. In addition, crystallinity and size of crystallized modified polycarbonate particles can be efficiently controlled to produce a high-molecular weight modified polycarbonate having uniform physical properties in the solid state polymerization.

Abstract: The present invention relates to a method for preparing polycarbonate resin, and more particularly to a method for effectively preparing polycarbonate resin having a large molecular weight in a short time under a melt polymerization condition using a catalyst system comprising phosphoranylidene ammonium salts, which is stable and maintains superior reactivity during melt polymerization and solid state polymerization.

Abstract: A method of preparing a high molecular weight polycarbonate resin is provided. In the method, a condensation polymerization process is used so that a mole fraction of arylcarbonate existing in a terminated group of a reaction side product having a degree of polymerization of less than 3 obtained as a result of transesterification and in a non-reacted diarylcarbonate is reduced. As a result, a high molecular weight polycarbonate can be obtained by solid state polymerization. A polycarbonate with an identical molecular weight can be produced in a substantially short time, compared with a polycarbonate produced through solid state polymerization without condensation polymerization. In addition, the non-use of a poisonous phosgene contributes to stability. Furthermore, quality polycarbonate may be guaranteed.

Abstract: Provided is a method of preparing styrene polymers, the method comprising: homogeneously mixing a styrene monomer; a cocatalyst mixture of Group 13 metal-containing organic metal compound cocatalyst and an inert organic solvent; and a catalyst mixture of a metallocene catalyst and the inert organic solvent using a high speed homogenizing mixer to obtain a homogenized mixture; and providing the homogenized mixture to a reactor to initiate polymerization. In this method, catalyst is quickly dispersed among monomers using a high speed homogenizing mixer so that formation of gel, which occurs when a syndiotactic styrene polymer is produced, can be fundamentally prevented. In addition, a styrene polymer prepared using the method has high activity, good stereoregularity, and uniform molecular distribution.

Abstract: The present invention relates to a method for producing (meth)acrylic acid comprising a process of recovering (meth)acrylic acid as an aqueous (meth)acrylic acid from a (meth) acrylic acid-containing gas mixture produced by the catalytic gas phase oxidation of at least one reactant selected from the group consisting of propane, propylene, isobutylene and (meth) acrolein, and a system usable for the method.

Abstract: The present invention provides a process of producing unsaturated acids from unsaturated aldehydes by fixed-bed catalytic partial oxidation in a shell-and-tube heat exchanger-type reactor, as well as a shell-and-tube heat exchanger-type reactor for use in the process. In the invention, second-stage reaction zone of mainly producing unsaturated acids by the catalytic vapor phase oxidation of an unsaturated aldehyde-containing gas mixture produced in a first-stage reaction zone with molecular oxygen is divided into two or more shell spaces by at least one partition. Each of the divided shell spaces is filled with a heat transfer medium, and the heat transfer medium in each shell space is maintained at isothermal temperature or a temperature difference of 0-5° C. Also, in order to protect catalyst layers from a highly exothermic reaction, the process is performed at a limited temperature difference between the temperature at a hot spot and the temperature of the heat transfer medium.

Abstract: The present invention provides a process of producing unsaturated aldehydes and unsaturated acids from olefins by fixed-bed catalytic partial oxidation in a shell-and-tube heat exchanger-type reactor. In this process, the reactor comprises a first-step reaction zone of mainly producing the unsaturated aldehydes, a second-step reaction zone of mainly producing the unsaturated acids, or both the two zones. The first-step reaction zone is divided into two or more zones by a partition. Each of the divided shell spaces is filled with a heat transfer medium, and the heat transfer medium in each shell space is maintained at isothermal temperature or a temperature difference of 0-5° C. The temperatures of the heat transfer media in each of the divided shell spaces are set to increase in the moving direction of reactants. In order to facilitate the removal of heat generation at a location where the partition is placed, a reaction inhibition layer is disposed in the first-step reaction zone.