Separation of o- and p-chlorobenzoic acids: Hydrotropy and precipitation

The aqueous solubilities of o- and p-chlorobenzoic acids (CBAs) in different concentrations of sodium butyl monoglycol sulphate (NaBMGS) solutions at 25 and 45 degrees C are determined by the weight disappearance method. The precipitation of o- or p-CBA by dilution with water from their single component NaBMGS solution is carried out in a 2 L agitated jacketed crystallizer. The crystal size distributions (CSDs) of the precipitated solids are determined using a multichannel Coulter counter. The effects of significant process variables, namely, temperature, water addition flow rate and speed of agitation on the CSDs are investigated in a series of batch experiments. The results are analysed by the method of s-plane analysis and correlations between the nucleation and growth rates are presented.