Polyoxometalate catalyzed oxidative desulfurization of diesel range distillates from waste tire pyrolysis oil

Abstract

The properties of tire pyrolysis oil are similar to diesel oil, but the high sulfur content in the pyrolysis oil limits its use in diesel engines. In this work, taking the boiling point range of traditional diesel oil as the cutting temperature, a fraction in the temperature range of 190–350 °C was obtained by distillation of tire pyrolysis oil (TPO190–350°C). The sulfides in TPO190–350°C are mainly benzothiophene derivatives. And a simple and effective POM-based catalyst ([C16H33N(CH3)3]3PW4O24) has been used in the oxidation desulfurization process for the removal of sulfur compounds from the oil. The catalyst played the role of transferring reactive oxygen species atoms on H2O2 to sulfur compounds. The benzothiophene, dibenzothiophene, and 4,6-dimethyl-dibenzothiophene (500 ppm S) in model oil could be converted to the corresponding sulfone within 1 h at 40 °C. Even if the sulfur content was increased to 2000 ppm, the catalyst exhibited well catalytic performance under the same conditions. The catalyst could be recycled and reused with no loss of desulfurization efficiency. Distillation could effectively reduce the presence of olefins in the oil leading to reduce oxidation performance during the oxidation desulfurization process (ODS). In the subsequent desulfurization experiments of TPO190–350°C, a high desulfurization efficiency (91.28%) was achieved for TPO190–350°C, with initial sulfur contents of 11033 ppm declining to 961 ppm.