Process for the preparation and purification of monocyclic aromatic polycarboxylic acids or mixtures thereof

Claim 1

A PROCESS OF PRODUCING MONOCYCLIC AROMATIC POLYCARBOXYLIC ACIDS, COMPRISING THE STEPS OF TREATING CARBONIFEROUS MATTER AT ELEVATED TEMPERATURE WITH NITRIC ACID SO AS TO FORM A REACTION MASS INCLUDING DARK COLORED ORGANIC IMPURITIES AND LIGHT COLORED MONOCYCLIC AROMATIC POLYCARBOXYLIC ACIDS; DISTILLING-OFF THE RESIDUAL NITRIC ACID FROM THE THUS FORMED REACTION MASS; DIGESTING THE THUS REMAINING REACTION MASS WITH A SOLVENT SELECTED FROM THE GROUP CONSISTING OF WATER AND LOW BOILING POINT KETONES IN AN AMOUNT SUFFICIENT TO CAUSE DISSOLUTION OF SAID LIGHT COLORED MONOCYCLIC AROMATIC POLYCARBOCYLIC ACIDS IN SAID SOLVENT WHILE PREVENTING DISSOLUTION OF SAID DARK COLORED ORGANIC IMPURITIES THEREIN; SEPARATING THE UNDISSOLVED DARK COLORED ORGANIC IMPURITIES FROM THE THUS FORMED SOLUTION EVAPORATING SAID SOLUTION; AND RECOVERING A MIXTURE OF SUBSTANTIALLY PURE LIGHT COLORED MONOCYCLIC AROMATIC POLYCARBOXYLIC ACIDS.