Plastering Sponge with Nanocarbon-Containing Slurry to Construct Mechanically Robust Macroporous Monolithic Catalysts for Direct Dehydrogenation of Ethylbenzene

Nanocarbons have shown great potential as a sustainable alternative to metal catalysts, but their powder form limits their industrial applications. The preparation of nanocarbon-based monolithic catalysts is a practical approach for overcoming the resulting pressure drop associated with their powder form. In our previous work, a ploycation-mediated approach was used to successfully prepare nanocarbon-containing monoliths. Unfortunately, because there are no macropores in the monolith, it needs to be crashed into millimeter-sized particles before application. Therefore, developing a facile method for preparing mechanically robust nanocarbon-based macroporous monolithic catalysts is vital but still challenging. Herein, evoked by swallows building their nests, we report an approach for successfully preparing a mechanically robust nanodiamond-based macroporous monolith catalyst by plastering melamine sponge (MS) with a slurry composed of nanodiamonds (NDs) and poly(imidazolium-methylene) chloride (PImM) followed by an annealing process. The macroporous monolith catalyst (ND/NC_MS-NC_PImM) containing NDs well dispersed in N-doped carbon is mechanically robust with enriched macroscopic pores. It exhibits outstanding catalysis toward ethylbenzene to styrene through a direct dehydrogenation reaction with a high styrene rate in a steady state (5.50 mmol g^-1 h^-1) and high styrene selectivity (99.5%). ND/NC_MS-NC_PImM shows much higher activity than powder ND by 1.9 fold. In addition, this work solves the significant problem of large pressure drop encountered with conventional powdered nanocarbon catalysts in the flow reactor. This work not only creates an excellent nanodiamond-based macroporous monolithic ethylbenzene direct dehydrogenation catalyst but also presents a promising avenue for preparing other macroporous monolithic catalysts for diverse transformations.

Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts

The development of cost-effective, efficient, and novel catalytic systems is always an important topic for heterogeneous catalysis from academia and industrial points of view. Heteroatom-doped carbon materials have gained more and more attention as effective heterogeneous catalysts to replace metal-based catalysts, because of their excellent physicochemical properties, outstanding structure characteristics, environmental compatibility, low cost, inexhaustible resources, and low energy consumption. Doping of heteroatoms can tailor the properties of carbons for different utilizations of interest. In comparison to pure carbon catalysts, these catalysts demonstrate superior catalytic activity in many organic reactions. This review highlights the most recent progress in synthetic strategies to fabricate metal-free heteroatom-doped carbon catalysts including single and multiple heteroatom-doped carbons and the catalytic applications of these fascinating materials in various organic transformations such as oxidation, hydrogenation, hydrochlorination, dehydrogenation, etc.

Recent advances in metal-free heteroatom-doped carbon heterogeneous catalysts including the preparation methods and their catalytic applications in various organic reactions have been reported.

Oxidative Dehydrogenation of Ethylbenzene into Styrene by Fe-Graphitic Catalysts

Carbon-based catalysts have attracted much attention for the dehydrogenation (DH) of organic molecules, due to their rich active sites, high conversion efficiency, and selectivity. However, because of their poor stability at high operation temperature and relatively high cost, their practical applications have been limited. Here, we report a simple ball-milling-induced mechanochemical reaction which can introduce iron (Fe) and different functional groups (mostly stable aromatic C═O after heat-treatment) along the edges of graphitic nanoplatelets. The resulting Fe-graphitic nanoplatelets (Fe-XGnPs, X = H, C, N, or V) provide active sites for the oxidative dehydrogenation (ODH) of ethylbenzene into styrene. Among them, Fe-NGnPs (X = N) displayed the highest performance for styrene production at low temperature (∼11.13 mmol g^-1 h^-1, 450 °C) with high selectivity and durability.

Nitrogen-doped porous carbon materials: promising catalysts or catalyst supports for heterogeneous hydrogenation and oxidation

Developing novel and efficient catalysts is a critical step in common heterogeneous hydrogenation and oxidation reactions.

N-, P- and B-doped mesoporous carbons for direct dehydrogenation of propane

N-, P- and B-doped mesoporous carbons were used as metal-free catalysts in propane dehydrogenation, and their catalytic performances were influenced critically by the chemical structures and oxygen-containing groups in these carbons.

Activity studies of vanadium, iron, carbon and mixed oxides based catalysts for the oxidative dehydrogenation of ethylbenzene to styrene: a review

The activity of V, Fe and carbon based catalysts depends on V⁵⁺, Fe³⁺and active carbon sites. The mixed oxide catalysts show superior activity than individual oxides.