Free radicals induced ultra-rapid synthesis of N-doped carbon sphere catalyst with boosted pyrrolic N active sites for efficient acetylene hydrochlorination

Activated carbon-supported HgCl₂ catalysts have seriously impeded the development of the polyvinyl chloride (PVC) industry due to the sublimation of Hg species and environmental pollution problems. Herein, the template-free and organic solvent-free strategy was devised to synthesize non-metallic based nitrogen-doped carbon (U-NC) sphere catalyst for acetylene hydrochlorination. This green strategy via ultrasonic chemistry initiates resin crosslinking reactions between aminophenol and formaldehyde resin by free radicals, leading to the ultra-rapid formation of U-NC with remarkably high pyrrolic N content in only 5 min. This U-NC catalyst exhibited an outstanding space-time-yield (1.6 g_VCM·g_cat⁻¹·h⁻¹), even comparable to the reported metallic catalyst. By combining kinetic analysis, advanced characterizations, and density functional theory, it is found that the amount of pyrrolic N is in linear with C₂H₂ conversion, and pyrrolic N in U-NC can effectively improve acetylene hydrochlorination performance by mediating HCl adsorption. This work sheds new light on rationally constructing metal-free catalyst for acetylene hydrochlorination.