Confining Noble Metal (Pd, Au, Pt) Nanoparticles in Surfactant Ionic Liquids: Active Non-Mercury Catalysts for Hydrochlorination of Acetylene

Metal catalysts often encounter the dilemma of rapid deactivation due to reduction or particle aggregation/growth during the reaction. Here we reported an active and stable metal nanoparticles (NPs)/surfactant ionic liquid (IL) system for the catalytic hydrochlorination of acetylene. The NPs of Pd, Au, and Pt with a narrow size distribution and well-defined lattice fringes experienced in situ generation in the reaction medium of anionic surfactant carboxylate ILs (ASC-ILs). Benefiting from the high reactivity of NPs and the self-assembly property of ASC-ILs, an effective redox cycle between Pd⁰ and Pd^II was established to reduce the deactivation of metal catalysts. The Pd NPs/surfactant IL systems showed excellent catalytic activity toward acetylene hydrochlorination. An acetylene conversion of 93% and a selectivity of 99.5% were achieved with no discernible deterioration over a reaction time of 55 h. Furthermore, ASC-ILs were endowed with a unique property of the strong hydrogen-bond basicity, which was effective in absorbing and activating acetylene and HCl. This study manifests that metal NPs/surfactant IL systems are promising as substitutes for toxic mercury catalysts in the hydrochlorination of acetylene, and also is instructive for the stabilization of metal NPs.