Process design, simulation and experimental studies of heteroazeotropic batch distillation for phenol dehydration

Phenolic compounds are important groups of chemicals with many applications. Due to the strong affinity between phenols and water, the dehydration of phenolic compounds is often necessary and inevitable. The conventional method for phenol dehydration is the direct distillation without entrainers, leading to high phenol concentration (2–5 wt%) in wastewater and significant difficulty in subsequent wastewater treatment. In this work, heteroazeotropic batch distillation was studied by simulations and experiments to remove water from water-bearing phenols. By simulation, effects of entrainer type, operating pressure, number of theoretical stages, entrainer amount and decanter hold-up on dehydration efficiency were studied in detail. The results showed that the heteroazeotropic batch distillation using ethylbenzene as the entrainer yielded desirable dehydration results with many advantages. The wastewater generated in the dehydration process showed a much lower content of phenolic compounds than the direct distillation, greatly reducing the cost and difficulty of wastewater treatment. The energy consumption of heteroazeotropic distillation was also lower than the direct distillation. Batch distillation experiments were performed to validate the reliability of simulation results. The experimental results were in high agreement with simulations. The produced phenol products showed a water content of 470 ppm, and the content of phenolic compounds in wastewater was reduced to as low as 5.0 ppm. The heteroazeotropic batch distillation proposed in this study suggested an ideal strategy for phenol dehydration which is economically feasible and environmental-friendly.