Optimization of operating conditions in oxidation of dibenzothiophene in the light hydrocarbon model

Abstract

© 2014, Serbian Chemical Society. All rights reserved. In this research, the effects of process variables on the efficiency and mechanism of dibenzothiophene oxidation in formicacid/H2O2 system for deep desulfurization of a light hydrocarbon model were systematically studied by statistical modelling and optimization using response surface methodology and implementing the central composite design. A quadratic regression model was developed to predict the yield of sulfur oxidation as the model response. The model indicated that temperature was the most significant effective factor and suggested an important interaction between temperature and H2O2/sulfur ratio; at temperatures above 56 °C, more excess oxidant was necessary because of instability of active peroxo intermediates and loss of H 2 O 2 due to thermal decomposition. In contrast, the water hindrance effect of H 2 O 2 aqueous solution in desulfurization progress was more significant at temperatures bellow 56 °C. In the optimization process, minimizing H2O2/sulfur ratio and catalyst consumption for maximum yield of desulfurization was economically considerable. The optimal condition was obtained at temperature of 57 °C, H 2 O 2 /sulfur mole ratio of 2.5 and catalyst dosage of 0.82 mL in 50 mL solution of DBT in n-hexane leading to a maximum oxidation yield of 95% after 1 h reaction. Good agreement between predicted and experimental results (less than 4% error) was found.