Ultrasound-assisted oxidative desulfurization (UAOD) of Iranian heavy crude oil: Investigation of process variables

Abstract

The ultrasonic-assisted oxidative desulfurization (UAOD) process of an Iranian heavy crude oil was performed for the first time. The applied heavy crude oil was from the West Paydar Field, Iran. Its main properties included API gravity, 18.53 and sulfur content, 38638 ppm. Hydrogen peroxide, acetic acid, CuSO 4 , and acetonitrile were applied as oxidant, catalyst, phase transfer agent (PTA), and extraction solvent, respectively. The effects of different parameters, including ultrasound power at five levels, PTA amount at seven levels, catalyst amount at five levels, preheating temperature at three levels, reaction time at five levels, were investigated. Two scenarios of experiments were conducted in each section. The results indicated that increasing ultrasonic power, reaction time, and catalyst amount had positive influences on sulfur reduction. There was an optimal point in increasing PTA and preheating temperature. At the best conditions, including preheating temperature, 70 °C; acetic acid as catalyst, 4.8 wt%; hydrogen peroxide as oxidant, 2.92 wt%; reaction time, 10 min; CuSO 4 as PTA, 1 wt%; ultrasonic power, 7 W/ml, the sulfur reduction was 48.68 wt%. In addition, the influences of PTA type (CuSO 4 , FeSO 4 , FeCl 2 , FeCl 3 ), PTA size, the number of extraction stages at three levels, and multistage UAOD at three levels were evaluated. According to the results of this part, CuSO 4 showed the best performance. With increasing the number of stages of extraction and UAOD, sulfur removal increased from 48.68 wt% to 52.15 wt% and 53.55 wt%, respectively. Also, the comparison between UAOD and oxidative desulfurization (ODS) processes was performed. The results indicated that the sulfur reduction of UAOD process during 10 min was three times more than that of ODS process during 90 min. The results of this research revealed that UAOD process is effective for sulfur removal of heavy crude oil. • UAOD process is performed for Iranian heavy crude oil for the first time. • The effects of various parameters on UAOD process are systematically investigated. • The investigated parameters include power, PTA (type, amount, size), catalyst, time. • Also, the number stages (extraction, UAOD), UAOD and ODS comparison are evaluated. • At the best conditions, the sulfur removal of heavy crude oil was 53.35 wt%.