Review on oxidative desulfurization of fuel by supported heteropolyacid catalysts

Desulfurization of fuel has been an important issue in fuel refining process. Hydrodesulfurization, as a traditional and commercial desulfurization technique for removing sulfur compounds, has been widely researched for decades. But as the environmental policy implemented on fuel becoming stricter, it is more difficult to remove organic sulfur compounds by hydrodesulfurization technology. Therefore, non-hydrodesulfurization technologies developed rapidly in recent years. Among all novel desulfurization technologies, oxidative desulfurization (ODS) functions best with its mild reaction condition and efficient desulfurization capacity. Heteropolyacid (HPA) has been intensively investigated because the HPA has discrete ionic structure and high proton mobility, which makes it extremely promising in catalysis. As a result, HPA has been applied in a variety of synthetically selective transformations of organic substances and the ODS is one of them. However, HPA have shortcomings such as their high solubility in polar solvents and low specific surface area. To overcome these problems, many works have been done to combine heteropolyacids with other materials. The main derivatives of HPA used in ODS are supported heteropolyacid, phase transfer heteropolyacid catalyst and polyoxometalate based ionic liquid. The catalytic activity and reusability of HPA are substantially increased after modification. The works on heteropolyaicds for ODS from 2010 to 2019 will be summarized in this review.