Abstract: A method for purifying a crude (meth)acrylic acid obtained by a vapor phase catalytic oxidation method, characterized in that the crude (meth)acrylic acid having most parts of water and acetic acid removed therefrom, is fed to and distilled in a first distillation column of a purification system comprising first to third three distillation columns, the top fraction from the first distillation column is fed to and distilled in the second distillation column, the resulting top fraction is recovered as a high purity (meth)acrylic acid product, the bottoms from the first and second distillation columns are fed to and distilled in the third distillation column, and the resulting top fraction is fed to the first distillation column.

Abstract: A method for collecting acrylic acid is provided, which includes the step of collecting acrylic acid using an aqueous medium from a reaction gas containing acrylic acid obtained by catalytic vapor-phase oxidation of propane, propylene, and/or acrolein, the step being conducted so as to satisfy the following formula (1) (B/A)<1.25 (1) wherein A represents a weight fraction of acrylic acid to all condensable ingredients in the reaction gas before collecting acrylic acid and B represents a weight fraction of acrylic acid in bottoms of a collection device used in the step of collecting. According to the method, acrylic acid can be efficiently collected from the reaction gas containing acrylic acid obtained by catalytic vapor-phase oxidation.

Abstract: The invention provides a process for producing and/or purifying acrylic acid or methacrylic acid or an ester of any of these, wherein mixtures of high-boiling heavy ingredients (high-boiling matter mixtures) discharged from individual step units are classified by the content therein of (meth)acrylic acid and/or of the dimer thereof and handled. According to the invention, even when high-boiling matters which have been discharged from distillation columns, high-boiling-matter cracking reactors, and the like in a plant for producing (meth)acrylic acid and/or an ester thereof and are alike in liquid nature are mixed with each other in the same tank, no polymer precipitation occurs. The handling and storage thereof are hence easy. Consequently, tanks can be united into one, and the process is extremely advantageous in reducing the construction cost and the area necessary for equipment.

Abstract: The storage tank of the invention for an easily polymerizable compound is a storage tank having an acceptance piping and a delivery piping and is characterized by having a circulation line which directly connects the acceptance piping to the delivery piping or having circulation lines which respectively connect the acceptance piping to the storage tank and the storage tank to the delivery piping; the method of storing of the invention is characterized by storing an easily polymerizable compound in the storage tank while circulating the compound in the storage tank through the circulation line(s); the method of pipe jointing and apparatus therefor of the invention are a method of jointing pipes fitted to a handling apparatus in a production apparatus, storage apparatus, or the like for the purpose of transporting a corrosive liquid, the method being characterized in that the pipes are jointed with flanges, bolts, and nuts made of a material having resistance to corrosion by the corrosive liquid; the process fo

Abstract: Disclosed is a gas-insulated switchgear device, in which a space for dismantlement and inspection work which facilitates the dismantlement and inspection work of circuit breakers at the time of the occurrence of accidents of the circuit breakers are provided and an installation area for the gas-insulated switchgear device can be reduced. The gas-insulated switchgear device includes a pair of spaced apart main bus lines, three circuit breakers connected between the main bus lines, a common space for dismantlement and inspection work provided between two of the three circuit breakers, and branch bus lines provided above the common dismantlement and inspection work space using the common dismantlement and inspection work space and disposed in such a manner that insulatedly leading-out directions of the branch bus lines cross in order to balance voltage.

Abstract: A process for producing (meth)acrylic acid or (meth)acrylic acid esters, which comprises a reaction step comprising vapor phase catalytic oxidation of propylene, propane or isobutylene and, if necessary, a reaction step comprising an esterification step, characterized in that at the time when a high boiling mixture (hereinafter referred to as a high boiling material) containing a Michael addition product, is decomposed in a decomposition reactor to recover (meth)acrylic acids, while forcibly imparting a liquid flow in the circumferential direction to a liquid reaction residue in the decomposition reactor, the liquid reaction residue is discharged. In a process for recovering a valuable substance by thermally decomposing the high boiling material containing the Michael addition product of (meth)acrylic acids, it is possible to transfer the decomposition residue from the decomposition reactor to the storage tank without clogging, whereby a long-term continuous operation is possible.

Abstract: There is provided a process for producing (meth)acrylic acid and (meth)acrylic esters, which can be operated in a continuous and stable manner for a long period of time.

Abstract: The present invention provides a method for efficiently using an aqueous solution of (meth)acrylic acid at a low concentration formed in a production/storage step of (meth)acrylic acid. In the present invention, a (meth)acrylic acid derivative is produced by using as a raw material an aqueous solution of (meth)acrylic acid formed by one or both of: a device which reduces a pressure of a gas comprising (meth)acrylic acid in production of (meth)acrylic acid; and a device which collects (meth)acrylic acid from a gas comprising (meth)acrylic acid.

Abstract: Clogging of a distillation column by polymerization caused by a change of the production rate of (meth)acrylic acid, is prevented to carry out a stabilized operation over a long period. A process for producing (meth)acrylic acid, which includes a purification step wherein a (meth)acrylic acid-containing material to be purified is supplied to and distilled by a distillation column, wherein during a cut operation in which the production rate of (meth)acrylic acid is reduced by ?% relative to the production rate of (meth)acrylic acid during the ordinary operation, the liquid/gas flow rate in the distillation column is adjusted to be at least (100??/2)% of the liquid/gas flow rate during the ordinary operation.

Abstract: A storage tank for an easily polymerizable compound has acceptance piping and delivery piping with a circulation line directly connecting the acceptance piping to the delivery piping or with circulation lines respectively connecting the acceptance piping to the storage tank and the storage tank to the delivery piping. A method of storing an easily polymerizable compound in the storage tank includes circulating the compound in the storage tank through the circulation line(s), where the compound can be (meth)acrylic acid being produced and/or purified with the temperature of purified (meth)acrylic acid being supplied to or removed from the storage tank being regulated to not be higher than the temperature thereof in the tank. A method of joining pipes for-transporting a corrosive liquid using flanges, bolts, and nuts made of a material having resistance to corrosion by the corrosive liquid.

Abstract: The present invention provides a method for suppressing an undesirable polymerization reaction of (meth)acrylic acid in a purification step for producing (meth)acrylic acid and for avoiding troubles due to clogging of devices or the like, to thereby attain a stable continuous operation. The present invention provides a method for producing (meth)acrylic acid comprising: distilling a water-containing liquid of (meth)acrylic acid containing (meth)acrylic acid and water by using a distillation column in the presence of an azeotropic solvent boiling together with at least water to remove water from the water-containing liquid of (meth)acrylic acid through azeotropy with the azeotropic solvent, in which the water-containing liquid of (meth)acrylic acid is distilled in the presence of the azeotropic solvent after distillation by the azeotropic solvent is carried out in the distillation column.

Abstract: An oxidation reactor includes a reactor body, a manhole nozzle projecting from the reactor body, and a partition plate separating an inside of the manhole nozzle and an inside of the reactor body from each other. In an oxidation reactor including the reactor body and a nozzle projecting from the reactor body, there is provided a means for feeding an inert gas into the nozzle. In a process for producing (meth)acrylic acids by subjecting propane, propylene or isobutylene to catalytic gas-phase oxidation reaction in an oxidation reactor for producing (meth)acrolein or (meth)acrylic acid, the above oxidation reactor is used as the oxidation reactor. In a method for analyzing an easily-polymerizable compound by introducing a gas containing the easily-polymerizable compound into an analyzing apparatus through a sampling tube, a double tube is used as the sampling tube, and a heating medium is fed into an outer tube of the double tube.

Abstract: An object of the present invention is to provide that, in a process for the production of (meth)acrolein or (meth)acrylic acid by a gas-phase catalytic oxidation reaction of a substance to be oxidized such as propylene, propane, isobutylene and (meth)acrolein with molecular oxygen or molecular oxygen-containing gas using a multi-tubular reactor equipped with one or more catalyst layer(s) in a direction of tube axis, a sudden rise of temperature is suppressed even after changing the reaction condition for raising the reaction temperature for enhancing the production velocity whereby inactivation of the catalyst is prevented and a stable production is carried out.

Abstract: (1) In a gas-phase catalytic oxidation process for conducting gas-phase catalytic oxidation reaction using a fixed bed multipipe type reactor having reaction tubes filled with a catalyst while feeding a reaction raw gas thereinto, the catalyst is filled in each of the reaction tubes of the fixed bed multipipe type reactor to form two or more catalyst layers having different catalytic activities from each other in a direction of the oxidation reaction, and the catalyst layer disposed nearest to a reaction raw gas inlet of the reaction tube has a higher catalytic activity than that of the next catalyst layer adjacent thereto, or (2) in a process for producing (meth)acrolein or (meth)acrylic acid by subjecting a raw material of the (meth)acrolein or (meth)acrylic acid, and molecular oxygen or a molecular oxygen-containing gas to gas-phase catalytic oxidation reaction using a fixed bed multipipe type reactor having two or more catalyst layers in an axial direction of each of reaction tubes provided in the reactor

Abstract: In the stopping and starting operations of a distillation column used for producing (meth)acrylic acids according to the present invention, upon stopping the operation of the distillation column, the heating of a reboiler attached thereto is interrupted and then the reboiler is rapidly cooled; and/or upon starting the operation of the distillation column for production of the (meth)acrylic acids, an inner wall surface of the distillation column is heated to a temperature higher than a condensation temperature of the (meth)acrylic acids and the operation of the distillation column is started under the heated condition. According to the present invention, it is possible to early and safely stop the operation of the distillation column while preventing the occurrence of polymerization within the distillation column, and stably perform an operation for distillation of acrylic monomers for a long period of time.

Abstract: (1) In a gas-phase catalytic oxidation process for conducting gas-phase catalytic oxidation reaction using a fixed bed multipipe type reactor having reaction tubes filled with a catalyst while feeding a reaction raw gas thereinto, the catalyst is filled in each of the reaction tubes of the fixed bed multipipe type reactor to form two or more catalyst layers having different catalytic activities from each other in a direction of the oxidation reaction, and the catalyst layer disposed nearest to a reaction raw gas inlet of the reaction tube has a higher catalytic activity than that of the next catalyst layer adjacent thereto, or (2) in a process for producing (meth)acrolein or (meth)acrylic acid by subjecting a raw material of the (meth)acrolein or (meth)acrylic acid, and molecular oxygen or a molecular oxygen-containing gas to gas-phase catalytic oxidation reaction using a fixed bed multipipe type reactor having two or more catalyst layers in an axial direction of each of reaction tubes provided in the reactor

Abstract: A process for producing a (meth)acrylic acid compound, which comprises distilling acrylic acid, methacrylic acid (these will hereinafter generally be referred to as “(meth)acrylic acid”) or an ester thereof (these will hereinafter generally be referred to as “a (meth)acrylic acid compound”) in a distillation column to obtain a purified (meth)acrylic acid compound, characterized in that in the course of operation of the distillation column including suspension and resumption of the operation, the distillation column is washed with water and, thereafter, inside washing with an organic solvent and/or azeotropic distillation in the presence of the organic solvent is conducted. In some cases, washing with alkaline water may be added prior to the washing with water. Washing of the distillation column for separating and purifying a crude (meth)acrylic acid compound, can be carried out easily.

Abstract: The present invention removes impurities inhibiting storage stability of (meth)acrylic acid or stability in polymerization of (meth)acrylic acid when (meth)acrylic acid is used as a raw material, to thereby stabilize (meth)acrylic acid. A total concentration of aromatic hydrocarbons each having 8 to 10 carbon atoms in a (meth)acrylic acid composition is controlled to less than 2 ppm. The (meth)acrylic acid composition can be obtained by crystallizing (meth)acrylic acid from a crude (meth)acrylic acid composition containing the aromatic hydrocarbons, sweating the crystallized (meth)acrylic acid, and separating the (meth)acrylic acid remained as a crystal after the sweating.

Abstract: There is provided a process for purifying (meth)acrylic acid by efficiently removing transition metal components from crude (meth)acrylic acid containing the transition metal components as impurities. When the crude (meth)acrylic acid containing the transition metal components as impurities is contacted with the cation exchange resin to remove the transition metal components therefrom, water is previously added to the crude (meth)acrylic acid prior to contacting the crude (meth)acrylic acid with the cation exchange resin. In the preferred embodiment of the present invention, the transition metal component is manganese.

Abstract: A multitube reactor, wherein tubes having smaller tolerance between a nominal size and actual sizes are used as reaction tubes to stably perform a high yield reaction for a long period, a catalyst is filled into the reaction tubes so that the catalyst layer peak temperature portions of the reaction tubes are not overlapped with the connection sites thereof with baffles to effectively prevent hot spots from occurring and stably perform a reaction for a long period without the clogging of the reaction tubes, a heat medium and raw material gas are allowed to flow in the direction of a countercurrent and a specified type of catalyst is filled into the reaction tubes so that activity is increased from the inlet of the raw material gas to the outlet thereof to prevent the autooxidation of products so as to prevent equipment from being damaged due to the reaction, and, at the time of starting, gas with a temperature of 100 to 400° C.