Recovery of n-butanol from its Ternary Azeotropic Mixture with Methanol and Water

Abstract

This paper is one of the numerous efforts in reducing the organic content of effluent streams. The effluent is the top product of a distillation column. This distillate is a ternary azeotrope consisting of methanol, n-butanol and water. The feed to this distillation column is through a separator, separating as much organic content from the water as possible, leaving some quantity in the leaner phase. This separator was found to be under-designed. Redesigning drastically reduced the organic content of the leaner phase. Next, in order to separate as much n-butanol from methanol and water, and vice versa, as possible, the unit operation of Liquid-Liquid Extraction was utilized. Two solvents were tried, viz., toluene and mixed xylene. It was found that toluene not only gave better extraction results, but also, did not need to be separated from n-butanol as it could be reused and re-fed into the process at some point. Thirdly, it was also tried whether process parameter modification proved passable and could be used a fortiori. It was checked if vacuum operation of the process was admissible. The variation in the azeotropic composition with vacuum was first numerically checked using computer spreadsheets. These spreadsheets give information whether vacuum operation increased or decreased the organics in the effluent. It was found that reducing the pressure gives two-edged results. It reduces the loss of n-butanol to all intents and purposes; antithetically, it increases that of toluene. And the methanol just doesn’t form any azeotrope with water.