PRELIMINARY EVALUATION OF ALTERNATIVES TO DISTILLATION FOR ACETIC-ACID RECOVERY FROM TEREPHTHALIC ACID FLOWSHEETS

Acetic acid is presently recovered from terephthalic acid flowsheets by distillation. This paper documents a preliminary evaluation of extraction for its recovery and recycle. Experimental data show that the solvent has a selectivity for acetic acid-water of 5 for a 50 wt. percent acid solution and 60 for 5 wt. percent acid solution. Above 10 wt. percent extractant in the solvent, addition of extractant to the solvent has the combined effect of decreasing the solvent loss to the aqueous phase and decreasing the loading of water in the solvent. The high selectivities of the solvent for acid vs. water combined with the high relative volatility of the acid vs. the solvent imply that lower energy costs with an extraction flowsheet over distillation is likely.