Ionic-Liquid-Mediated Self-Regulation of Deposit Evolution in Ru-Catalyzed Liquid-Phase Acetylene Hydrochlorination

Abstract Ru-based liquid-phase catalysts are promising for mercury-free acetylene hydrochlorination, yet deactivation by carbonaceous deposits remains a critical challenge. This study shows that deposit evolution, rather than deposit amount alone, governs catalyst stability. Ru/TMS and Ru-IL/TMS (TMS = sulfolane; IL = [BTPP]Cl) were compared through control experiments and multiscale characterization. Both systems generated carbonaceous deposits, denoted CD and CD-IL, respectively, through acetylene oligomerization, chain growth, and aromatization near Ru sites. CD evolved into highly aromatic, thermally stable, hydrogenolysis-resistant carbon, whereas CD-IL remained more disordered, defect-rich, and hydrogenolysis-susceptible. [BTPP]Cl dynamically regulates oligomeric and PAH-like precursors while maintaining a chloride-rich local environment, thereby retarding deep dehydrogenation, cross-linking, and condensation. This self-regulated evolution enabled Ru-IL/TMS to operate stably for 600 h, versus ∼160 h for Ru/TMS. These findings show that regulating deposit evolution, rather than merely suppressing formation, offers a strategy for designing durable mercury-free hydrochlorination catalysts.