無水7タル酸よリテレ7タル酸の合成
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概要
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For synthesis of terephthalic acid from Phthalic anhydride by the Henkel process in industrial scale, studies have been made on its reaction vessel and recovering of potassium. The result was able to clarify on its reaction mechanism. The reaction vessel for a continuous reaction as a thin film on a steel belt was simple in operation and good result was obtained. For recovering of potassium, a direct one or two step exchange of Phthalic acid and potassium terephalate, sulfurous acid gas method and carbon dioxide method were tested. The resut indicated that sulfurous acid gas-calcium hydroxide method and neutralization-sulbimation separation method of using two moles Phthalic anhydride, concentration of monopotassium phthalate, and heating of the solid phase above 300°c for separation of dipotassium phthalate and Phthalic anhydride for their separation by sublimation gave good result. Studies on the reaction products indicated that the end product of reaction around 360°c was terephthalic acid, a small amount of Phthalic anhydride and large amount of benzoic acid. Further continuance of the reaction indicated the formation of benzoic acid dianion as an intermediate product from the fact that there was little or no formation of benzoic acid and from the consideration of melting point of potassium benzoate, potassium phthalate and potassium terephthalate. Metal (Cd, Pb, and Zn) carbonates as effective catalyst showed far lower decomposition temperature for conversion into oxide and liberation of carbon dioxide than other metal carbonates. Therefore, those which showed catalytic activity were considered to have an ability of holding decarboxylated carbon dioxide without losing it out of the system.