A novel process for recovery of phenol from alkaline wastewater: laboratory study and predesign cost estimate

A novel process for recovery of phenol from alkaline wastewater has been demonstrated at laboratory scale. The process is based on the polymer-supported phase-transfer-catalyzed reaction of alkaline phenols with benzoyl chloride dissolved in toluene. The reaction conducted in a triphase system at room temperature generates phenyl benzoate, which is subsequently recovered as the product. Phosphonium ion immobilized on chloromethyl polystyrene crosslinked with divinylbenzene was used as the catalyst. Laboratory experiments were conducted in a batch slurry reactor and a fixed-bed reactor to assess the suitability of a particular reactor type to practical applications. An aqueous phase to organic phase volume ratio of 1:2 was found to be suitable. The slurry reactor was found to be more attractive for the reaction. Based on the result of experiments in batch slurry reactors and other processing steps, a conceptual flow scheme was proposed for the process, and a predesign cost estimate was made. As such, the treatment cost of the proposed process is higher than that of the usual solvent extraction process, but the capital cost is comparable. However, the cost of the recovered phenyl benzoate will more than offset the higher treatment cost. This is reflected in a payback period of 1.5 years for the proposed process as compared to 2.5 years for the typical solvent extraction process. For industrial applications, a pilot-plant study needs to be performed for a detailed cost analysis.