Nitrogen-Doped Carbons with Hierarchical Porosity via Chemical Blowing Towards Long-Lived Metal-Free Catalysts for Acetylene Hydrochlorination

Porous nitrogen-doped carbons (NCs) are sustainable alternatives to the toxic mercury-based acetylene hydrochlorination catalysts applied in the manufacture of polyvinyl chloride. However, the application of NCs as metal-free catalysts is hampered by their insufficient durability under industrially relevant process conditions. In particular, pore blockage leads to accelerated deactivation of NCs compared to the state-of-the-art precious metal-based systems. Herein, we develop a salt template-assisted synthesis strategy coupled with chemical blowing to tune the textural properties of NCs, while preserving the N-content and speciation. The addition of metal salts (i. e., Mg(OAc)(2) or CaCO3) enhances gas evolution, leading to an increased formation of micro- and mesopores, while the in-situ generated CaO/CaCl2 and MgO/MgCl2 develop auxiliary pore networks. Micropores are easily blocked during acetylene hydrochlorination, but meso- and macropores are structurally stable, enhancing the lifetime of hierarchical NCs by ca. 50 times compared to their non-templated analogues, rivaling the stability of benchmark metal-based catalysts.