Optimization of Naphthalene Extraction from Cracked Fuel Oil (CFO) in Shazand Petrochemical Complex

The cracked fuel oil product (CFO) derived from the olefin process is a complex mixture of the polycyclic aromatic hydrocarbons (PAHs) with 13 to 31% of naphthalene. In recent years, new applications for industrial and extremely pure naphthalene have been developed. Therefore, an alternative method of the distillation and catalytic hydrogenation must be chosen to reduce the economic cost and environmental impact resulting from the increase in demand for pure naphthalene. In the present study, purification of naphthalene from a CFO using the crystallizations followed by the solvent extraction process has been compared with the distillation method. The Box-Behnken design (BBD) as a method of the response surface methodology (RSM) was applied to minimize the number of runs and process optimization. The crystals’ purity of 73.71% and the crystallization yield of naphthalene of 96.73% have been achieved at an optimum cooling temperature of 25 °C, which at lower temperatures, the yield of naphthalene recovery will be lower. The melting temperature, the extraction yield and the purity of naphthalene were 80.13 °C, 97.36% and 99.42%, respectively under optimum operational conditions of extraction temperature of 15.08 °C, phenol/methanol volume ratio of 1.01, and solvent/feed volume ratio of 1.72. The statistical results indicated that the response surface quadratic model for our parameters was significant (p-value <0.0001) and a perfect correlation (R²=0.9989) between the statistical model (Design-Expert) and experimental data was found. Furthermore, according to the analysis of variance (ANOVA), the temperature of extraction and its interaction with the phenol to methanol volume ratio has a significant impact on the melting temperature. Also, the solvent mixture will be highly recoverable from methanol and phenol. In general, our results suggest that the introduced approach is an efficient and promising technique for producing native naphthalene from CFO.