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

Abstract

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.

Design of carbon supports for metal-catalyzed acetylene hydrochlorination

“…Upon exceeding a region of optimal C 2 H 2 interaction, the initial activity stagnates and even decreases. This behavior, in line with the Sabatier principle 41 , has also been observed over metal-free N-doped carbon catalysts in acetylene hydrochlorination 30 . Accordingly, to optimize acetylene interaction, the porous properties and the total oxygen content can be adjusted.…”

“…Accordingly, sufficient acetylene interaction could be verified as general activity descriptor for metal-based hydrochlorination catalysts, explaining why supports like C1 or CeO 2 are impractical for this reaction. Notably, this correlation between activity and optimal acetylene interaction has also been identified for metal-free hydrochlorination catalysts, such as N-doped carbons (NC) 30 . To exclude the possibility that carbon, besides effectively adsorbing acetylene, may further serve as a carbon source in the catalytic cycle, 13 C labeled NC was synthesized from labeled aniline and tested under typical reaction conditions (see Supplementary Discussion for details) 29 .…”

Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

“…It is worth noting that BE was much lower than other adsorbents such as CB in adsorption experiments. The possible reason is that bentonite has fine particles and micropores are easily blocked in the process of Hg adsorption [ 36 , 37 , 38 ], while CB has the common characteristics of biochar and bentonite, forming a bimodal adsorption system with mesopores leading to micropores [ 11 ], so it has higher adsorption capacity for Hg 2+ , and its adsorption mechanism for Hg 2+ needs further experimental study.…”

Constructing the single‐site of pyridine‐based organic compounds for acetylene hydrochlorination: From theory to experiment

“…It is generally accepted that N doping carbon with heteroatoms is an effective approach to improve its catalytic activities. [ 67–76 ] Zhao et al introduced an strategy for preparation of N,P‐codoped carbonbased materials (NP‐C600), which has shown unexpectedly high catalytic activity in acetylene hydrochlorination. [ 73 ] Li group prepared nitrogen‐doped ordered mesoporous carbons (N‐OMCs).…”