Abstract: The present invention provides an industrially easy and economical method for purification of acrylic acid which enables to efficiently eliminate impurities from a crude acrylic acid containing aldehydes as the impurities while the formation of acrylic acid polymer is inhibited. The method for purification of acrylic acid includes the step of distilling a crude acrylic acid which is charged with an aldehyde treatment chemical, wherein the concentration ratio of furfural to acrolein by weight in the crude acrylic acid is adjusted so as to satisfy the following equation: (furfural concentration by weight)/(acrolein concentration by weight)?100.

Abstract: For use in a process for the production of (meth)acrylic acid comprising at least a step for the reaction of (meth)acrylic acid by catalytic gas phase oxidation and a step for the absorption thereof, a method for preventing an effluent gas pipe from blocking is disclosed, which method is characterized by causing part or the whole of the gas discharged from the step for absorption, while being circulated via the effluent gas pipe to the step for the reaction or being discarded, to be subjected to temperature elevation and application of pressure and/or mist separation. Particularly by setting the temperature of the waste gas from the absorption column at a level in the range of 30-70° C.

Abstract: In a method for distilling (meth)acrylic acid and/or (meth)acrylic ester, the method has the step of uniformly distributing a supply liquid in a distillation tower over an entirety of a horizontal cross sectional area in the distillation tower. A distillation apparatus for distilling (meth)acrylic acid and/or (meth)acrylic ester in a distillation tower has a supply element for supplying the supply liquid into the distillation tower. The supply element is formed with at least two supply ports through which the liquid is supplied into the distillation tower.

Abstract: The present invention provides an industrially easy and economical method for purification of acrylic acid which enables to efficiently eliminate impurities from a crude acrylic acid containing aldehydes as the impurities while the formation of acrylic acid polymer is inhibited.

Abstract: For use in a process for the production of (meth)acrylic acid comprising at least a step for the reaction of (meth)acrylic acid by catalytic gas phase oxidation and a step for the absorption thereof, a method for preventing an effluent gas pipe from blocking is disclosed, which method is characterized by causing part or the whole of the gas discharged from the step for absorption, while being circulated via the effluent gas pipe to the step for the reaction or being discarded, to be subjected to temperature elevation and application of pressure and/or mist separation. Particularly by setting the temperature of the waste gas from the absorption column at a level in the range of 30-70° C.

Abstract: The present invention provides a process for producing (meth)acrylic acid by gas-phase catalytic oxidation, which comprises cooling and condensing a (meth)acrylic acid-containing reaction product gas to obtain a crude aqueous (meth)acrylic acid solution; cooling the aqueous solution to deposit the impurities contained in the aqueous solution, as solid matter; separating the solid matter; and then extracting and separating (meth)acrylic acid from the purified aqueous (meth)acrylic acid solution obtained. Unlike the conventional processes in which (meth)acrylic acid is extracted and separated from a crude aqueous (meth)acrylic acid solution, the present process can avoid various troubles caused by the impurities contained in the crude aqueous (meth)acrylic acid solution, for example, generation of scum and the like, and therefore can produce (meth)acrylic acid at a higher purity than in the conventional processes.

Abstract: A process for the production of acrylic acid by the two-stage catalytic vapor-phase oxidation of propylene with molecular oxygen, the first stage for oxidizing propylene to produce mainly acrolein and the second stage for oxidizing acrolein to produce mainly acrylic acid, which process comprises supplying to the first-stage reaction a raw gas containing a saturated aliphatic hydrocarbon having 1 to 5 carbon atoms in an amount in the range of 5 to 70% by volume, carbon dioxide in an amount in the range of 3 to 50% by volume, and the aliphatic hydrocarbon and the carbon dioxide in a total amount in the range of 20 to 80% by volume and further containing steam in an amount in the range of 0.5 to 8 mol per mol of propylene.