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Alumina-supported copper chloride serves as an industrial catalyst for ethylene oxychlorination, resulting from its high activity and selectivity. A better understanding of the detailed active site structure and reaction mechanism is highly desired. The present work aims to explore the dependence of the structure of active sites and the adsorption of ethylene on differently sized (CuCl2)n(n= 1–4) clusters supported by γ-Al2O3. The effect of the support facets (i.e., (110) and (100) surfaces) on the interface structures between the active component CuCl2and the support was also investigated. The stronger CuCl2–support interaction was found on the (110) surface compared to the (100) surface, which is attributed to the stronger Lewis acidity of Al of the (110) surface. The adsorption strength of (CuCl2)n)(n= 1–4) clusters becomes weak with the increment of cluster size on the (110) surface. The cluster size has a profound influence on the interaction between ethylene and the clusters. Ethylene binds to a copper atom on the small clusters (i.e., CuCl2and (CuCl2)2), while it extracts two chlorine atoms to form dichloroethane from the large clusters (i.e., (CuCl2)3and (CuCl2)4), which explains the high activity of catalysts with high loadings upon exposure to ethylene. The effects of cluster size and alumina facets on the short d-band center and the Bader charge of the active sites result in the distinct formation energy of the chlorine vacancy and the interaction energy between C2H4and the clusters. Thus, an improved catalyst could be achieved by the modification of the surface electronic structure via fine-tuning the support or adding promoters.

Systematic and in-depth understanding of size- and metal-dependent activity plays a pivotal role in nanocatalysis for rational design of highly efficient catalysts. Herein, we report an approach combining microkinetic modeling with a truncated octahedron model to explore the size- and metal-dependent activity, using steam methane re-forming on metallic (M = Rh, Ni, Pt, and Pd) nanoparticles as a model system. It is found that activity is inversely proportional to particle size, and this size-dependent activity results from the fraction change in surfaces with distinct activity. M(211) is the active surface, and the increased M(211) surface fraction with decreasing particle size results in enhanced activity. In addition, the metal-dependent activity is elucidated, with the activity following Rh > Ni > Pd ∼ Pt. Moreover, the intrinsic size- and metal-dependent activity are analyzed on the basis of dominant reaction pathway, which are fundamentally related to C-metal and O-metal binding ability, respectively.

The mechanism of CH4formation during Fischer–Tropsch synthesis on cobalt has been studied. DFT, kinetic isotope effect and kinetic analyses are combined to discriminate between the possible reaction routes of CH4formation on Co catalysts. Nine direct reaction mechanisms were proposed from 21 elementary steps. They were first screened by DFT calculations in which the activation energies as well as the free energy profiles in each direct mechanism were compared, resulting in a reduction to six reaction mechanisms. Additional reduction was based on kinetic analysis where the reaction order was used as a descriptor. Subsequently, the kinetic isotope effect (KIE) values were calculated and compared to our previous SSITKA results. Finally, the dominating reaction route was suggested, which follows the initial elementary steps with H-assisted CO activation to form HCOH viaHCO as an intermediate. It then proceeds through HCOH dissociation to CH followed by stepwise hydrogenation to CH4.