Synergetic ultrasound assisted catalytic oxidative extractive desulfurization of tire pyrolysis oil employing sustainable protic deep eutectic solvents

•Novel protic deep eutectic mixtures synthesized and thermophysical properties determined.•Ultrasound-assisted oxidative extractive desulfurization of tire pyrolysis oil accomplished.•Synergetic effect between ultrasound and DES on the process elucidated.•The physicochemical parameters and calorific value of resulting TPO was determined. One-pot ultrasound-assisted selective oxidative extractive desulfurization (UA-SOEDS) of tire pyrolysis oil (TPO) was carried out with sustainable protic deep eutectic solvent (pDES) synthesized with quaternary ammonium salts as HBA and organic acids as HBD. The Tetrabutyl ammonium chloride and malic acid-based pDES with moderate viscosity resulted in a maximum Sulphur removal of (92.6 % (w/v)). A central composite design-based optimization of essential variables (US time (12 min), US temperature (333.15 K), US power (1.2 kW) and pDES/TPO ratio (22.5 % v/v)) was carried out resulting in an effective sulfur removal rate of (93.6% w/w). The pDES post extraction was recovered with the addition of isooctane and reused for consecutive cycles of UA-SOEDS process, loosing its characteristic oxidative extraction property after 3rd cycle (68.53%). The chromatographic analysis confirmed the presence of long-chain hydrocarbons in the oxidized TPO which confirms its property as a good fuel. The physicochemical properties and the calorific value of the resulting base oil were determined making it a suitable candidate as an alternative green fuel meeting the international standards of soluble Sulphur.