Abstract: There is provided a method for preventing clogging in an apparatus for handling (meth)acrylic acid or esters thereof which is capable of inhibiting occurrence of clogging in nozzles or conduits connected to a gas-phase portion of the apparatus and ensuring a stable continuous operation of the apparatus for a long period of time. The method for preventing clogging in an apparatus for handling (meth)acrylic acid or esters thereof, comprises blowing a gas having a polymerization inhibiting action into a nozzle or conduit connected to a gas-phase portion of the apparatus, wherein said gas having a polymerization inhibiting action, which is blown into the nozzle or conduit, has a temperature not less than a temperature of the gas-phase portion.

Abstract: A decomposition reaction apparatus or distillation apparatus for acrylic acid in which a column bottom liquid heated in a reboiler (5) is supplied from a supply port (1a) provided on a side wall of a column body 1 comprises: a top plate (12a) above the supply port (1a); and an impingement plate (12b) provided vertically to the top plate (12a), for preventing scattering of the column bottom liquid to a supply direction. The top plate (12a) is provided such that the top face of the top plate (12a) is inclined downward from a base end to a tip end. The present invention allows: suppression of formation of a polymerized product due to flowing of a liquid or gas heated in a reboiler into a column with a simple structure; and a stable continuous operation of column equipment over a long period of time.

Abstract: The present invention provides a process for catalytic vapor phase oxidation which prevents runaway reaction or early deterioration of a catalyst, in the production of (meth)acrylic acid or the like from propylene or isobutylene by the catalytic vapor phase oxidation process using a multi-tubular reactor, which can lead to the production thereof constantly in high yield for a long period of time.

Abstract: (Meth)acrolein or (meth)acrylic acid is collected by bringing a reaction gas (1) containing (meth)acrolein or (meth)acrylic acid obtained through a vapor-phase catalytic oxidation reaction into contact with an aqueous solution as a collecting solvent in a collecting tower main body (2). The reaction gas (1) is supplied to the collecting tower main body (2) from two nozzles (2c) facing each other, and is caused to collide in the collecting tower main body (2). According to the present invention, (meth)acrolein or (meth)acrylic acid can be efficiently collected from a gas containing (meth)acrolein or (meth)acrylic acid while preventing polymerization.

Abstract: A crude acrylic acid-containing liquid containing acrylic acid is distilled in a distillation column to obtain a condensate of acrylic acid having an acrylic acid purity of 90% or more, and an oxygen-containing gas (air) containing oxygen is supplied to the condensate of acrylic acid in a reflux tank for receiving the condensate of acrylic acid. The present invention can efficiently produce high purity (meth)acrylic acid by preventing formation of a polymerized product of (meth)acrylic acid in the condensate obtained in production of high purity (meth)acrylic acid through distillation.

Abstract: There is provided a method for storing (meth)acrylic acid or (meth)acrylic esters in a storage tank for receiving or discharging the (meth)acrylic acid or (meth)acrylic esters, which is capable of storing the (meth)acrylic acid or (meth)acrylic esters for a long period of time. According to the method of the present invention, upon storing the (meth)acrylic acid or (meth)acrylic esters in the storage tank for receiving or discharging the (meth)acrylic acid or (meth)acrylic esters, a concentration of suspended particulate matters contained in a gas phase portion of the storage tank is controlled to not more than 0.01 mg/m3.

Abstract: A method for transporting an easily polymerizable liquid by a pipeline having branches, wherein among pipelines branched at a branch point, one pipeline which may not be used over a long period of time, is provided with a valve to close the pipeline, within 500 mm from the branch point.

Abstract: In an apparatus capable of distilling and refining an easily polymerizable substance, piping is performed so that when a strainer in action is switched to a backup strainer, the strainer can be switched after removing air in the backup strainer to replace air in the backup strainer with a discharge liquid of a pump. According to the apparatus, switching the strainers installed on an upstream side of the pump for extracting a liquid of a vacuum distillation column, which distills and refines the easily polymerizable substance, can be performed with no trouble during operation of the distillation column. When the apparatus includes a device for measuring a differential pressure between an upstream side and a downstream side of the strainer in action, two or more strainers installed in parallel can be switched at proper times and the easily polymerizable substance can be produced efficiently.

Abstract: In a process for producing (meth)acrylic acid comprising contacting a reaction gas containing (meth)acrylic acid obtained by gas-phase catalytic oxidation with an absorbent solvent to prepare a (meth)acrylic acid solution; and introducing the (meth)acrylic acid solution into a distillation column to purify (meth)acrylic acid, after a dissolved oxygen concentration in the (meth)acrylic acid solution to be introduced into the distillation column is adjusted to not less than 12 ppm by weight, the (meth)acrylic acid solution is fed to the distillation column. In addition, upon an azeotropic dehydration distillation step, a phenol-based polymerization inhibitor is fed to an azeotropic dehydration distillation column from a position not lower than a raw material feed stage thereof, and a copper-based polymerization inhibitor is fed to the azeotropic dehydration distillation column from a position lower than the raw material feed stage.

Abstract: In the process for producing (meth)acrolein or (meth)acrylic acid, which comprises feeding a raw material of the (meth)acrolein or (meth)acrylic acid, and a molecular oxygen-containing gas mixed with a diluting gas and compressed by a compressor, to an oxidation reactor to conduct a catalytic gas-phase oxidation reaction therebetween; feeding the obtained reaction gas to an absorption column to contact with water; recovering an aqueous solution of the (meth)acrolein or (meth)acrylic acid from a bottom of the absorption column and an exhaust gas from a top of the absorption column; and recycling a part or whole of the thus recovered exhaust gas to use as the diluting gas, the temperature of the mixed gas at a suction inlet of the compressor is controlled to a temperature higher than a dew point thereof. According to the process of the present invention, the compressor is prevented from suffering from clogging or damage thereto.

Abstract: The present invention provides a process for producing purified (meth)acrylic acid by subjecting crude (meth)acrylic acid containing maleic acids and aldehydes as impurities to distillation, the said process comprising, prior to the distillation, the following steps: (A) adding hydrazines to the crude (meth)acrylic acid at a temperature of not less than a melting point of acrylic acid and not more than 50° C. to react the maleic acids with the hydrazines; (B) heat-treating the reaction solution obtained in the above step (A) at a temperature of 60 to 90° C. to convert the reaction product into a substance soluble in the reaction solution; and (C) adding hydrazines to the thus heat-treated reaction solution obtained in the above step (B) at a temperature of not less than the melting point of acrylic acid and not more than 50° C. to react the aldehydes with the hydrazines, thereby producing a substance soluble in the reaction solution.

Abstract: In an acrylic acid production process which comprises the step of producing acrylic acid by catalytic vapor-phase oxidation of propane, propylene, and/or acrolein; and purifying the acrylic acid produced in the step of producing with distillation in the presence of the polymerization inhibitor for preventing polymerization of the acrylic acid, a viscosity at 20° C. of the bottoms which comprises the polymerization inhibitor, discharged in the step of purifying, is adjusted to 2 Pa·s (2,000 cP) or less and the polymerization inhibitor is extracted using an aqueous medium. According to the method, in an acrylic acid production process, an extraction operation for recovery of the polymerization inhibitor can be continuously conducted in a stable manner.

Abstract: In an apparatus capable of distilling and refining an easily polymerizable substance, piping is performed so that when a strainer in action is switched to a backup strainer, the strainer can be switched after removing air in the backup strainer to replace air in the backup strainer with a discharge liquid of a pump. According to the apparatus, switching the strainers installed on an upstream side of the pump for extracting a liquid of a vacuum distillation column, which distills and refines the easily polymerizable substance, can be performed with no trouble during operation of the distillation column. When the apparatus includes a device for measuring a differential pressure between an upstream side and a downstream side of the strainer in action, two or more strainers installed in parallel can be switched at proper times and the easily polymerizable substance can be produced efficiently.

Abstract: In the purification and distillation step of acrylic acid (including (meth)acrylic acid), stable continuous operation for a long period is enabled by inhibiting the undesirable polymerization reaction of acrylic acid thereby to prevent the device from a trouble such as clogging.

Abstract: There is provided a method for handling high-viscosity substances discharged from a production process of acrylic acid or esters thereof by gas-phase catalytic oxidation, which method is improved such that upon transporting the high-viscosity substances in a molten state to a storage tank through a pipeline, the retention or clogging of the high-viscosity substances in the pipeline can be effectively prevented without adding a solvent thereto, resulting in smooth transportation thereof through the pipeline.

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: There is provided a process for producing (meth)acrolein or (meth)acrylic acid which is capable of avoiding stoppage of operation of a plant for production thereof as a whole due to failure of a low-boiling fraction separation step in the process and ensuring a continuous stable operation of the plant, and has excellent economical aspects.

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: There is provided a process for producing (meth)acrolein or (meth)acrylic acid which is capable of avoiding stoppage of operation of a plant for production thereof as a whole due to failure of an oxidation reaction step in the process and ensuring a continuous stable operation of the plant, and is excellent in economical aspects.

Abstract: The present invention provides a process for recovering liquid chemical products, in which the residual liquid chemical products remaining in respective handling devices in a chemical production facility can be efficiently and safely recovered therefrom without leakage thereof out of the system. In the process for recovering liquid chemical products in a chemical production facility according to the present invention, the chemical products are withdrawn from the handling devices through bottom discharge pipes (14), (15), (16) and (17) thereof, directly collected by the gravity thereof into a common inclined collection pipe (13) located at a position lower than the bottom discharge pipes and connected to the bottom discharge pipes, and then delivered by the gravity thereof through the inclined collection pipe (13) to a recovery tank (1) located at a position lower than the inclined collection pipe and connected to a lower end of the inclined collection pipe.