The conversion from syngas derived from non-petroleum recourses to liquid fuels and chemicals via Fischer–Tropsch synthesis (FTS) is regarded as an alternative and potential route. Developing catalyst with controllable particle size and clarifying size effect are of significance to promote the process. Herein, we engineered carbon-encapsulation structure to restrict particle growth but avoid strong metal–support interactions. The prepared carbon-encapsulated nanoparticles (Fe@C) showed a superior catalytic activity compared with conventional carbon-supported nanoparticles (Fe/C). By tuning particle size from 3.0 to 9.1 nm, a volcano-like trend of iron time yield (FTY) peaked at 2659 μmol·g_Fe⁻¹·s⁻¹ is obtained with an optimum particle size of 5.3 nm. According to temperature-programmed reduction and desorption results, a linear relationship between apparent turnover frequency and CO dissociation capacity was established. The enhanced CO dissociative adsorption along with weakened H₂ activation on larger nanoparticles resulted in higher C₅₊ selectivity. This study provides a strategy to synthesize carbon supported metal catalysts with controllable particle size and insight into size effect on Fe-based catalytic FTS.

Lignin utilization is a potential approach for replacing fossil energy and releasing the environment pressure. Herein, we synthesized a series of novel Cu-based catalysts, Cu@NS-SiO₂ (NS = nano sphere) and alkali metals (Na, K, Rb, and Cs) doped Cu@NS-SiO₂, and applied them in hydrodeoxygenation reaction of anisole. High Cu dispersion was presented on all catalysts. The modification of alkali metals on Cu@NS-SiO₂ significantly enhanced the electron density of Cu sites in the following order: Cs > Rb > K > Na, among which Cs decreased the Cu 2p_3/2 binding energy most (by 0.7 eV). Moreover, the modification did not substantially affect the geometric structure of Cu species. This regulable electronic environment of Cu sites was crucial for selective deoxygenation and inhibiting the hydrogenation of aromatic rings in anisole, and thus promoted the selectivity of benzene. Compared with Cu@NS-SiO₂ (~59%), the highest benzene selectivity was obtained on Cs/10Cu@NS-SiO₂ at ~83%.