Revealing the Synergetic Effect of a Ce-Modified MoP Triphasic Composite in Naphthalene Hydrogenation

The advancement of highly efficient and robust catalytic systems for the deep hydrogenation of polycyclic aromatic hydrocarbons is crucial for clean fuel production. The primary challenge is derived from the inadequate capacity for deep hydrogenation, necessitating catalysts that effectively activate hydrogen and sustain high throughput. To address these limitations, this study presents a Ce-modified molybdenum phosphide (xCeMoP) catalyst, which spontaneously assembles into a triphasic composite structure, comprising MoP, CePO4, and MoO2. Cerium incorporation fulfills multiple roles, including the transformation of the MoP phase into an electron-enriched state via electronic modulation, while the coexisting MoO2 phase acts as a structural matrix that stabilizes and highly disperses the active MoP nanoparticles, thereby facilitating hydrogen dissociation. Additionally, the electronic interaction between Ce and MoP induces oxygen vacancies in the CePO4 phase (CePO4–OV), providing primary sites for strong naphthalene adsorption. The synergy among these three phases creates an optimized hydrogenation environment. The optimal catalyst, 0.45CeMoP, achieved complete naphthalene conversion, exceeding 99% selectivity to decalin under 200 °C, 4 MPa H2 with a high WHSV (21 h–1), and a considerably increased stability (maintaining its activity and selectivity over 30 h of continuous operation), which outperforms the catalytic performance reported in the literature. Deeper mechanistic analysis reveals that naphthalene adsorption on CePO4–OV constitutes the rate-limiting step for the xCeMoP with a specific range of Ce/Mo ratios, whereas hydrogen dissociation capability on MoP becomes decisive when the Ce/Mo ratio deviates from this range. This work establishes a practical strategy for constructing high-performance transition-metal phosphide catalysts through multiphase synergy, offering a promising approach for advanced fuel upgrading with high processing capacity.