Process for the purification and formulation of o-phthalaldehyde

Abstract

Improved process for the purification and formulation of o-phthalaldehyde in which crude o-phthalaldehyde, obtained by cleavage of an acetal of o-phthalaldehyde by means of acidic hydrolysis, is, optionally by adding an aqueous basic solution, adjusted to a pH of from 1 to 8, and then, after phase separation has taken place, water is distilled off from the phase which contains the aldehyde with very short thermal stress of less than 1 minute at a pressure of between 100 mbar and atmospheric pressure and a temperature of from room temperature to 180° C. on a thin-layer overhead evaporator and o-phthalaldehyde is then stripped off from the distillation bottom which remains with very short thermal stress of less than 1 minute at a pressure of from 0.5 to 50 mbar and a jacket temperature of from 80 to 80° C. via a thin-layer evaporator and the resulting o-phthalaldehyde melt is pelleted at atmospheric pressure and a temperature of from 60 to 80° C., giving pale yellow o-phthalaldehyde in high purity and storage-stable form.

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