Catalytic transformation of light alkanes could have considerable practical value, yet remains one of the most challenging areas in catalysis research due to the inertness of the C–H bond. Here, we proposed an efficient ammodehydrogenation (ADeH) catalytic system for the direct C–N linkage between light alkanes and ammonia for CH3CN and H2 (CO x free) production. This breakthrough is achieved over bifunctional metal-modified HZSM-5 catalysts, through the tandem dehydrogenation–amination–dehydrogenation mechanism. We show that ethane ADeH over the Pt/HZSM-5 catalyst can be realized under atmospheric pressure at temperatures as low as 350 °C. The specific rate of CH3CN is ∼60 μmol/(g min), and the selectivity is up to 99% under such mild conditions. The yield of CH3CN increases with increasing temperature; however, the selectivity decreases due to the formation of HCN, C2H4, and CH4. Additionally, the Pt/HZSM-5 catalyst is coke-resistant during the ADeH owing to the strong interaction between NH3 and the acid sites of the catalyst. We anticipate that the proposed ADeH could be extended for the transformation of various n/iso-alkanes with tunable selectivity to alkene and nitriles.

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Minimizing Pt loading without sacrificing catalytic performance is critical, particularly for designing cost-efficient hydrocarbon transformation catalysts. Here, we show that ultralow-loading (0.001–0.05 wt %) Pt- and Zn-functionalized HZSM-5 catalysts, prepared through simple ion exchange and impregnation, are highly active and stable for light alkane dehydroaromatization (DHA). The specific activity of benzene, toluene, and xylene is up to 8.2 mol/gPt/min (or 1592 min–1) over the 0.001 wt % Pt–Zn2/HZSM-5 catalyst during ethane DHA at 550 °C under atmospheric pressure. Additionally, such bimetallic Pt x –Zn y /HZSM-5 catalysts are highly stable in contrast to the monometallic Pt/HZSM-5 catalysts. The rate constant of deactivation (k deactiv), according to the first-order generalized power law equation model, for the bimetallic catalysts is up to 120 times lower than that of the monometallic counterparts, depending on the Pt loading. This breakthrough is achieved through the formation of the [Pt1–Zn n ]δ+ hybrid cluster, instead of Pt0 cluster–proton adducts, in the micropores of the ZSM-5 zeolite.

Water-dispersible Fe 3 O 4 nanoparticles with diameters of 4.2 ± 0.6, 6.1 ± 0.8, 8.1 ± 1, and 10.4 ± 1 nm were prepared through the polyol method and employed as the precursors of Fe 3 O 4 /Al 2 O 3 catalysts to study the size-dependent activity. We identified that the activity of the catalysts in NH 3 decomposition (driven by both thermal and dielectric barrier discharge plasma) increased with increasing Fe 3 O 4 particle size. The turnover frequencies (TOFs) were increased from 0.9 to 5.8 s −1 with an increasing Fe 3 O 4 precursor size from 4.2 to 10.4 nm during the thermocatalytic decomposition. A quite similar "particle size effect" was also observed for the plasma catalytic decomposition, although lower TOF was observed. Additionally, reaction-induced catalyst reconstruction was identified during the early-stage of the catalytic decomposition and can be attributed to the nitridation of FeO x to Fe x N. Our results provide new evidence for the "structure-sensitivity" of the catalytic NH 3 decomposition.

Ethane ammoxidation to acetonitrile and ethylene over the Co/HZSM-5 catalysts was revisited based on both transient and steady-state performance evaluation to elucidate the structure/reactivity relationships. We suggested that the exchanged Co 2+ cation encapsulated in the zeolite favors the formation of acetonitrile and ethylene, whereas nanosized cobalt oxide particles without close proximity with the HZSM-5 only favor CO 2 formation. Excess Brønsted acid sites of the zeolites may act as a reservoir for NH 3 , which inhibits the CO 2 formation through the NH 3 -mediated oxidative dehydrogenation mechanism. According to the transient kinetic analysis, the time constants τ from the back-transient decay for NH 3 and CO 2 are both 7.7 min, which decreased to 2.7 min for acetonitrile and further decreased to 3−4 s for ethane, ethylene, and O 2 . Assuming first-order reaction kinetics, the rate constants for the formation of acetonitrile and CO 2 are 0.37 and 0.13 min −1 , respectively, from their corresponding reactive intermediates.