Selective Benzene Hydrogenation over Ru Catalysts in Multi-Aromatic Mixtures

Abstract

Ruthenium catalysts supported on diatomite (Ru/D) with varying loadings (0.5–1.5 wt.%) were synthesized and evaluated for the selective hydrogenation of aromatic compounds. Characterization by SEM, TEM, EDX, XRD, and BET revealed that the diatomite support retains its highly porous structure after Ru deposition, enabling uniform dispersion of Ru nanoparticles. EDX confirmed Ru incorporation, while XRD indicated the presence of highly dispersed Ru nanoclusters below the detection limit. Textural analysis showed a gradual decrease in surface area (60–45 m² g⁻¹) and pore volume (0.08–0.07 cm³ g⁻¹) with increasing Ru content, consistent with partial pore filling. Hydrogenation studies demonstrated that catalytic activity increased with Ru loading, with 1.5% Ru/D exhibiting the highest benzene hydrogenation rate (≈20×10⁻⁶ mol.s⁻¹). Benzene hydrogenation followed Arrhenius behavior, yielding an apparent activation energy of ~60 kJ mol⁻¹. Toluene and o-xylene hydrogenation showed slower kinetics due to steric and electronic effects of methyl substituents, while selectivity studies on a mixture of aromatics indicated nearly complete benzene conversion (94%) with minimal hydrogenation of substituted aromatics (toluene 14%, o-xylene 2%).