Ionic liquid-induced surface enrichment of Pt catalyst enables maximized atom utilization for mercury-free vinyl chloride synthesis

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Maximizing the atomic utilization efficiency of precious metals is crucial for developing high-performance industrial catalytic processes. An effective strategy to realize this goal involves precisely localizing metal active sites on the catalyst surface to enhance their accessibility and utilization. This study successfully constructed a surface-enriched platinum-based supported ionic liquid phase (SILP) catalyst for efficient and stable mercury-free synthesis of vinyl chloride monomer (VCM). Through a pre-assembly strategy employing specific ionic liquids, we precisely controlled the spatial distribution and electronic structure of Pt species, thereby fabricating a Pt-IL2/AC catalyst (where IL2 is tetrabutylphosphonium chloride and AC is activated carbon) in which Pt is preferentially enriched at the interfacial region to form highly exposed Pt 2 + active centers. Compared to the catalyst with a uniform bulk distribution of Pt species, the surface-enriched structure demonstrated superior catalytic performance. This configuration achieved a 50% reduction in Pt usage while maintaining high activity in the acetylene hydrochlorination reaction. Combined characterization and theoretical calculations revealed that the phosphorus atoms in IL2 drive the migration and stabilization of Pt species toward the surface through intermolecular interaction. Simultaneously, IL2 acts as an "HCl reservoir" by preferentially adsorbing HCl, while Pt sites selectively activate acetylene molecules. This spatial segregation of reactants effectively prevents chloride-induced deactivation of the Pt active sites, significantly enhancing catalyst stability. This study establishes a new paradigm for designing high-performance SILP catalysts.