In-situ construction of spherical N-doped carbon loaded with catalytic tungsten semicarbide nanoparticles for highly efficient sulfur removal from fuel oils

Abstract

Recently, transition-metal carbides (TMCs) have been developed as good catalyst candidates for oxidation desulfurization (ODS) reactions. However, improving their stability in strong oxidizing media remains a challenge. Herein, a W₂C catalyst protected by spherical N-doped carbon was constructed in-situ through a facile one-step thermal annealing process using phosphotungstic acid and zinc phthalocyanine microsphere (ZnPcMS) as the W and carbon sources, respectively. During annealing, the spherical N-doped carbon matrix (SNC) was simultaneously derived from ZnPcMS and combined closely with the in-situ formed W₂C, preventing W₂C from oxidation. The W₂C/SNC catalyst system, when combined with H₂O₂ as the oxidant, exhibits remarkable ODS performance. Desulfurization of model fuel oils can be achieved with 100 % efficiency within 25 min with a small H₂O₂ to S molar ratio of 3. Moreover, W₂C/SNC possesses superior reusability. A non-free radical oxidation mechanism is suggested for the ODS reaction based on radical scavenging tests. The as-prepared W₂C/SNC microspheres could serve as potential effective ODS catalysts.