Intensified desulfurization of Iraqi light gas oil using Pd/zeolite Nano-catalyst in an oscillatory helical baffled reactor

Deep oxidative desulfurization (ODS) of real light gas oil under mild operating conditions is required to satisfy stringent global environmental standards (<10–15 ppm S). However, conventional biphasic ODS processes in batch stirred reactors suffer from severe liquid-liquid mass transfer limitations and prolonged reaction durations (50–60 min). This study investigates a process-intensified continuous desulfurization system combining an ultrasonically dispersed Pd/Beta-Zeolite nano-catalyst with a custom-designed Oscillatory Helical Baffled Reactor (OHBR) applied to straight-run Iraqi light gas oil (Cin = 624 ppm S). The Pd/Zeolite nano-catalyst (6.0 wt% nominal active Pd loading on support, 1.5 wt% catalyst dosage relative to oil phase, Si/Al = 25, SBET = 113.3 m 2 /g, mean pore diameter = 6.22 nm) was synthesized via ultrasonic-assisted impregnation to ensure high dispersion of active PdO nanoparticles. Continuous ODS experiments were conducted across a multi-variable domain: reaction temperatures (40, 60, 80 °C), fluid oscillation frequencies (0.4, 0.8, 1.2 Hz at 15 mm amplitude), and residence times (4, 8, 12 min) using H 2 O 2 as oxidant (O/S = 4.0). Effluent oil was extracted with acetonitrile (1:1 v/v) to remove oxidized DBTO 2 sulfones prior to total sulfur analysis via MWDXRF (ASTM D7039). Formal kinetic fitting (pseudo-first-order) and activation energy (Ea) calculations across operating frequencies were systematically performed. Under optimized conditions (80 °C, 1.2 Hz, 12 min residence time), a maximum sulfur removal efficiency of 93.11 % was achieved, reducing residual sulfur content to 43 ppm. This performance represents a 5-to-7-fold reduction in reaction duration compared to conventional stirred batch reactors. Kinetic modeling demonstrated pseudo-first-order behavior ( R 2 > 0.85). Increasing oscillation frequency from 0.4 to 1.2 Hz reduced the apparent activation energy from 18.82 kJ/mol to 9.17 kJ/mol, confirming that high-shear fluid oscillation significantly lowers the energy barrier. The synergistic integration of an acidic, mesoporous Pd/Beta-Zeolite nano-catalyst with oscillatory fluid dynamics in an OHBR column provides an exceptionally fast, energy-efficient, and mass-transfer-free continuous process for petroleum desulfurization, establishing a robust foundation for industrial scale-up.