Method for recovering para-hydroxybenzaldehyde

Claim 1

IN A PROCESS FOR MAKING ORTHO- AND PARA-HYDROXYBENZALDEHYDES BY REACTION OF PHENOL AND CHLOROFORM ACCORDING TO THE REIMER-TIEMANN REACTION, WHEREIN THE ORTHO-HYDROXYBENZALDEHYDE IS SEPARATED FROM THE REACTION PRODUCT LEAVING A RESIDUE CONTAINING PARA-HYDROXYBENZALDEHYDE, THE STEPS WHICH CONSIST IN DISSOLVING THE RESIDUE IN AN AQUEOUS ALKALI METAL HYDROXIDE SOLUTION OF AT LEAST 2 WEIGHT PER CENT CONCENTRATION, DILUTING THE SOLUTION WITH WATER AND NEUTRALIZING THE SAME WITH A STRONG MINERAL ACID, WHEREBY THE PARA-HYDROXYBENZALDEHYDE REMAINS DISSOLVED AS SOLUTE AND ALKALI SOLUBLE BY-PRODUCT SUBSTANCES ARE PRECIPITATED, SEPARATING THE PRECIPITATE FROM THE SOLUTION, PASSING THE SOLUTION CONTAINING THE PARAHYDROXYBENZALDEHYDE AS SOLUTE INTO CONTACT WITH A SALT OF A STRONGLY BASIC QUATERNARY AMMONIUM ANION EXCHANGE RESIN, WHEREBY PARA-HYDROXYBENZALDEHYDE IS SORBED BY THE ANION EXCHANGE RESIN AND IS THUS REMOVED FROM THE SOLUTION, SEPARATING THE SOLUTION FROM THE RESIN AND WASHING THE RESIN WITH A WATER-MISCIBLE ORGANIC SOLVENT FOR THE PARA-HYDROXYBENZALDEHYDE, WHEREBY THE SORBED PARAHYDROXYBENZALDEHYDE IS ELUTED FROM THE ANION EXCHANGE RESIN.