VERFAHREN ZUR ISOLIERUNG VON P-HYDROXYBENZALDEHYD.

摘要

Process is for isolation of p-hydroxybenzaldehyde (I) from a reaction mixt. obtd. by oxidn. of p-cresol (II) with O2 or O2-contg. gas in MeOH in presence of NaOH or KOH and a manganese, nickel, chromium or cobalt salt. The process comprises: (i) treating the reaction mixt. with water; (ii) heating theobtd. soln.; (iii) filtering off the obtd. ppte. of hydrated Mn, Ni, Cr or Co oxide; (iv) distilling off MeOH from the filtrate; (v) cooling the remaining aq. soln.; and (vi) allowing (I) to crystallise as the Na or K salt. Alternatively the process comprises: (i') spray-drying the reaction mixt.; (ii') dissolving the soluble components of the residue in hot water; (iii') filtering off the undissolved hydrated Mn, Ni, Cr or Co oxide; and (iv') crystallising (I) as Na or K salt by cooling the filtrate. A further alternative process comprises: (i'') diluting the reaction mixt. with MeOH; (ii'') filtering off the undissolved hydrated Mn, Ni, Cr or Co oxide; (iii'') spray-drying the filtrate; (iv'') dissolving the residue in hot water; and (v'') crystallising (I) as Na or K salt by cooling the soln.