| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method to detect the end point of chlorination reaction by a sure method, without introducing excessive phosgene gas and enabling easy instrumentation of the process. SOLUTION: The chlorination method by introducing phosgene gas into a reaction vessel charged with an organic carboxylic acid to produce the corresponding carboxylic acid chloride comprises the introduction of phosgene gas into the reaction vessel at a constant rate, the suction of by-produced gas to keep the pressure of the reaction vessel to a level lower than atmospheric pressure by≥0.2 kPa, preferably by 0.2-1.0 kPa, and the stop of the supply of phosgene when the pressure in the reaction vessel is abruptly reduced by the stop of the generation of hydrogen chloride gas and carbon dioxide gas formed as by-products of the phosgenation reaction. The reaction end point is detected by the abrupt pressure drop. COPYRIGHT: (C)2009,JPO&INPIT
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