Application of response surface methodology (RSM) for optimizing and statistical analysis of ultrasound-assisted oxidative desulfurization (UAOD) of an Iranian heavy crude oil

Abstract

In this study, optimization and statistical analysis of oxidative desulfurization (ODS) of an Iranian heavy crude oil (HCO) by applying ultrasonic waves were performed. The investigated HCO was from the West Paydar Field of Iran (sulfur: 38638 ppm, viscosity: 78.76 cSt (20 °C), API: 18.53). The process was performed in the presence of acetic acid (catalyst), hydrogen peroxide (oxidant), and copper sulfate (PTA, phase transfer agent). The studied parameters included power (10–15 W/ml), temperature (60–80 °C), PTA (0–1 wt%), and catalyst (4.8–19.2 wt%). The processing time was 10 min. Acetonitrile was an extraction solvent. The experimental design was performed based on Box Behnken design (BBD) and consisted of 27 experiments. RSM was applied to model the response and to investigate the effects of one factor, parameter interactions, and optimization. A quadratic polynomial equation was presented for the model of HCO sulfur reduction. Based on the results, power, PTA, and catalyst had significant effects on the response. The regression coefficient of 0.9273 indicated a good agreement between the experimental results and the model results. Optimization results showed that under optimal conditions including power: 14.63 w/ml, temperature: 72.47 °C, PTA: 0.79 wt%, and catalyst: 4.84 wt%, desulfurization was 45.10 wt%.