Energy-saving extractive distillation process for the separation of close-boiling 2, 6-xylenol and p-cresol mixture

Abstract

1) Background

2,6-xylenol and p-cresol are widely used in medicine synthesis, which are both important raw materials in chemical engineering. It is shown significant economic benefits to separate 2,6-xylenol and p-cresol. Owing to the extremely relative volatility between 2,6-xylenol and p-cresol, it is difficult to separate the two phenolic compounds through conventional distillation.

2) Methods

The results of vapor–liquid equilibrium analysis, COSMO-SAC and reduced density gradient result are used to investigate molecular interaction in the separation system, indicating diethylene glycol (DEG) as the optimal solvent. Accordingly, we propose an energy-saving extractive distillation process with DEG as an efficient entrainer for the separation of 2,6-xylenol and p-cresol. Total annual cost (TAC) and CO₂ emission are investigated for optimization and estimation of the proposed process. In addition, three energy-saving scenarios for further reductions in TAC and CO₂ emission are proposed.

3) Significant Findings

Compared with the benchmark process, the TAC and CO₂ emission of the energy-saving design vapor recompression heat pump assisted extractive distillation separation sequence B are reduced by 26.18 % and 49.18 %, respectively, which indicates that the considerable industrial potential of the proposed design.