Desulfurization of Spent Tire Pyrolysis Oil and Its Distillate via Combined Catalytic Oxidation using H₂O₂with Formic Acid and Selective Adsorption over Al₂O₃

This paper reports an experimental investigation into the desulfurization of a spent tire pyrolysis oil and its distillate using a combined catalytic oxidative and selective adsorption method. The oxidative desulfurization (ODS) experiments were carried out in a batch reactor using H2O2-formic acid as oxidant. The effect of reaction temperature, time, and oil to H2O2-formic acid ratio on the percentage of sulfur removal was studied. The oil samples after ODS were treated using Al2O3 as an adsorbent in a batch reactor at 25 °C and atmospheric pressure. The oil samples were analyzed using inductively coupled plasma-optical emission spectrometry for sulfur content and gas chromatography-mass spectrometry and gas chromatography with sulfur chemiluminescent detection for chemical compositions and sulfur species. The ODS successfully converted the sulfur compounds to sulfoxides and sulfones but exhibited only moderate sulfur removal efficiency because sulfoxides and sulfones were dissolved in the oil and cannot be easily extracted by water. Al2O3 was effective in adsorbing sulfoxides and sulfones. A maximum of 81 and 84% sulfur removal were achieved for the raw pyrolysis oil and distillate, respectively, using combined ODS and Al2O3 adsorption. After three desulfurization cycles, the sulfur adsorption capacity of Al2O3 decreased from 0.31 to 0.22 mg S g-1 Al2O3, still exhibiting high sulfur removal ability.