Study on Optimal Conditions of Oxidative Desulfurization over Hierarchical CoAPO-5 Catalysts Using Response Surface Method

The present study focuses on the improvement of desulfurization rate in the oxidative desulfurization using hierarchical CoAPO-5 molecular sieve as a catalyst by response surface method. Firstly, the catalytic properties of microporous and hierarchical CoAPO-5 were compared, and hierarchical CoAPO-5 with better catalytic performance was selected for further investigation. Then, the reaction conditions were further optimized by response surface method. In the response surface method, five factors including reaction temperature, reaction time, catalyst dosage, extractant dosage and oxidant dosage affecting desulfurization rate were screened and the conditions for oxidative desulfurization were optimizing by applying Box–Behnken design. The fitting second-order polynomial equation, which was based on experimental results, was employed to predict desulfurization rate and verified by model diagnostic plots. According to the T and P values in the analysis of variance, it is found that the fitting model is significant, and the interaction between reaction temperature, reaction time, and extractant dosage is significant. The optimal conditions for oxidative desulfurization were found through three-dimensional surface and two-contour graph. In this case, the desulfurization rate reached 79.8%.