PHASE-RELATIONS OF O-CHLOROBENZOIC AND P-CHLOROBENZOIC ACIDS IN HYDROTROPE SOLUTIONS

The separation of chlorobenzoic acids from their mixtures of o- and p- components in hydrotrope solutions was investigated. The aqueous solub ilities of o- and p-chlorobenzoic acids in different concentrations of sodium cumene sulfonate and sodium butyl monoglycol sulfate solutions at different temperatures were determined by the mass disappearance m ethod. The ternary solid-liquid-phase equilibrium diagrams for the o-c hlorobenzoic acid + p-chlorobenzoic acids + water system with sodium c umene sulfonate and sodium butyl monoglycol sulfate as hydrotropes, in corporating several hydrotrope isoplethal curves and the two-component saturation and eutectic tie lines, were constructed. The sensitivity and feasibility of the proposed process are examined by carrying out s olubilization and equilibrium precipitation experiments with the mixtu res of various compositions, including the eutectic composition. With both these hydrotropes it was possible to enrich p-chlorobenzoic acid significantly in the product crystalline phase from the eutectic compo sition in a single stage. Highly pure (>99.0%) crystals of chlorobenzo ic acid were obtained from precipitation of noneutectic mixtures of o- and p-chlorobenzoic acids in their primary crystallization region.