Abstract: Provided is a method of purifying hydrochloric acid by removing an organic substance having a boiling point of ?25° C. to 120° C. under atmospheric pressure from a first organic substance-containing hydrochloric acid that contains the organic substance and has a hydrogen chloride concentration higher than an azeotropic hydrogen chloride concentration under atmospheric pressure. The method includes the step of subjecting a second organic substance-containing hydrochloric acid to distillation using a distillation tower under atmospheric pressure, to distill out the organic substance from a top of the distillation tower. The second organic substance-containing hydrochloric acid is obtained by mixing the first organic substance-containing hydrochloric acid and water or dilute hydrochloric acid and has the hydrogen chloride concentration lower than the azeotropic hydrogen chloride concentration under atmospheric pressure.

Abstract: Provided is a method of purifying hydrochloric acid by removing an organic substance having a boiling point of ?25° C. to 120° C. under atmospheric pressure from an organic substance-containing hydrochloric acid that contains the organic substance and has a hydrogen chloride concentration higher than an azeotropic hydrogen chloride concentration under atmospheric pressure. The method includes the step of subjecting the organic substance-containing hydrochloric acid to distillation using a distillation tower at an operation pressure set such that an azeotropic hydrogen chloride concentration under the operation pressure is higher than the hydrogen chloride concentration of the organic substance-containing hydrochloric acid, to distill out the organic substance from the top of the distillation tower.

Abstract: The present invention concerns a method for producing acrylic acid which involves subjecting an acrylic acid-containing aqueous solution obtained by catalytic vapor phase oxidation of propylene and/or acrolein to evaporation whereby an acrylic acid-containing vapor is obtained; and subjecting the acrylic acid-containing vapor to azeotropic dehydration. The present invention offers a number of advantages including a reduce amount of polymer that may adhere to the surface of an azeotropic dehydration column, a low-blowing separation column or an in a high-boiling separation column in a plant for producing acrylic acid. Consequently, the production plant can be operated for a long time without stopping operations.

Abstract: Disclosed is a process for producing a methacrylate polymer, wherein a monomer feed composed of methyl methacrylate or a mixture of at least 70 weight % of methyl methacrylate and not more than 30 weight % of one or more vinyl monomers copolymerizable with methyl methacrylate is continuously bulk polymerized in a substantially perfect mixing state to give a polymer composition having a polymer content of 40-70% by weight in a continuous manner, which comprises carrying out the bulk polymerization in the reactor which is filled up with the polymer composition leaving substantially no gas phase therein and which is maintained in a thermally insulated state allowing substantially no exchange of heat with the external environment at a polymerization temperature of 120.degree.-180.degree. C.