Mechanochemistry assisted oxidative desulfurization of high-sulfur petroleum coke over HPMo coupled binary deep eutectic solvent

Abstract

As the product in the coking of residual oil, the high-sulfur petroleum coke (HSPC, S > 3.0 wt%) has drawn increasing interest for the preparation of graphite electrodes in the steelmaking industry in recent years. How to effectively reduce the sulfide content of HSPC to produce low-sulfur petroleum coke (LSPC, S < 1.0 wt%) with high value is the research hotspot, but remains a huge challenge in the petroleum processing industry. Herein, a novel mechanochemistry-assisted HSPC oxidative desulfurization strategy was proposed with the amide based binary deep eutectic solvent (DES) as the extractant and solvent, and commercial grade phosphomolybdic acid (HPMo) and H₂O₂ used as catalyst and oxidant, respectively. The novelty of this method lied in the pretreatment of petroleum coke by ball milling, which increased the specific surface area of HSPC, thereby exposing more sulfur sites for the accessibility and reaction with H₂O₂ and reactive sites, and thereafter significantly enhancing the desulfurization rate of HSPC. The sulfur content of HSPC can be remarkably decreased from 4.46 wt% to 0.51 wt% under the reaction temperature of 60 °C due to the coupling effect between HPMo and DES, which represents the record-high desulfurization rate (88.6 %) and is strikingly higher that the state-of-the-art catalysts reported under the similar conditions so far. This work proposes a new avenue for design and preparation of advanced desulfurization catalyst for petroleum coke in the future.