Shifting Acetylene Hydrochlorination From the Gas to the Liquid Phase: Vinyl Chloride Production in Bichloride-Based Ionic Liquids

Abstract

Herein, [NEt3Me]2[PdCl4] is reported as a highly active catalyst for the mercury-free hydrochlorination of acetylene to vinyl chloride, resulting from the combination of the bichloride-based ionic liquid [NEt3Me][Cl(HCl)n] with PdCl2. Replacing gaseous HCl with the bichloride shifts the reaction in the liquid phase increasing the process safety by pressure reduction and achieves a turnover frequency of TOF = 110 molVCM h−1 molPdCl2−1 matching the productivity of state-of-the-art heterogeneous systems. Additionally, [NEt3Me]2[PdCl4] shows remarkable long-term stability and can be re-used over ten reaction cycles (200 h in total) without any problems due to its resistance to reduction by acetylene and coking as revealed by kinetic, theoretical, and spectroscopic investigations. Finally, initial catalytic studies demonstrate promising outcomes for applications of the bichloride-based ionic liquids with other noble metals, like platinum, if disproportionation phenomena, as observed for gold, do not occur.