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In this work, we report a carbon-mediated strategy to construct supported Co-MnO x nano-interfacial catalyst that enables highly selective synthesis of long-chain linear α-olefins (C 5+ =) via the Fischer-Tropsch (FT) reaction. The co-impregnation of glucose as the carbon precursor and metal salt aqueous solution over SiO 2 followed by pyrolysis and oxidation creates a catalyst with stable and rich Co-MnO x nano-interfaces after reduction and under FT conditions, which are convincingly revealed from characterizations of the catalysts at different stages. The optimal catalyst is stable for over 400 h without an observably decreased CO conversion, and the highest space-time yield of C 5+ = is achieved to be 0.79 g·g Co −1·h−1, which are mainly originated from the suppressed sintering of metallic Co and favored CO adsorption/dissociation with a reasonably inhibited H 2 co-adsorption. The simple procedure and broad availability of precursors make our developed strategy a practically important surface-engineering method capable of precisely fabricating stable nano-interfacial catalysts. [Display omitted] • Carbon-mediated method is explored for constructing Co-MnO x nano-interfacial catalyst. • The developed Co-MnO x catalyst is highly active and stable for Fischer-Tropsch reaction. • STY of 0.79 g·g Co −1·h−1 for C 5+ olefins is achieved over the optimal Co-MnO x catalyst. • Maximized Co-MnO x perimeter facilitates a high surface coverage ratio of CO* (C*)/H*. [ABSTRACT FROM AUTHOR]

Long-chain alcohols synthesis (LAS, C5+OH) from syngas provides a promising route for the conversion of coal/biomass/natural gas into high-value chemicals. Cu-Fe binary catalysts, with the merits of cost effectiveness and high CO conversion, have attracted considerable attention. Here we report a nano-construct of a Fe5C2-Cu interfacial catalyst derived from Cu4Fe1Mg4-layered double hydroxide (Cu4Fe1Mg4-LDH) precursor, i.e., Fe5C2 clusters (~2 nm) are immobilized onto the surface of Cu nanoparticles (~25 nm). The interfacial catalyst exhibits a CO conversion of 53.2%, a selectivity of 14.8 mol% and a space time yield of 0.101 g gcat−1 h−1 for long-chain alcohols, with a surprisingly benign reaction pressure of 1 MPa. This catalytic performance, to the best of our knowledge, is comparable to the optimal level of Cu-Fe catalysts operated at much higher pressure (normally above 3 MPa). Long-chain alcohols synthesis from syngas conversion is a promising route for the production of high-value chemicals. Here the authors show that a heterogeneous Fe5C2/Cu catalyst derived from layered double hydroxides precursor exhibits excellent performance with a space time yield of 0.101 g gcat−1 h−1 at a low pressure of 1 MPa. [ABSTRACT FROM AUTHOR]

As a prerequisite elementary step, carburization of iron oxides to form iron carbides is critically important to display activity for iron‐based Fischer–Tropsch synthesis catalysts. The positive role of the Cu promoter to advocate the reduction of the iron oxides has long been known. Nevertheless, its complex influence along the carburization of catalyst precursors remains controversial. Here, we resolve this decades‐long question by using a state‐of‐the‐art in situ X‐ray diffraction (XRD) method to elucidate the multi‐role of Cu promoter in modulation of carburization rate, composition of post‐carburization samples, and morphology evolution of prepared iron carbide particles under CO/He (v/v=2 %/98 %) and H2/CO/He (v/v/v=8 %/2 %/90 %) gaseous environment, by excluding the possible interference from promoter components other than Cu. We anticipate that this study enriches current tool box in the research of a specific promoter of the Fischer‐Tropsch synthesis catalysts. In situ seeing is believing: The complex influence of Cu promoter along the carburization of iron catalyst precursors has been elucidated by using a state‐of‐the‐art in situ X‐ray diffraction (XRD) method. Particularly, the multi‐role of Cu promoter in modulation of carburization rate, composition of post‐carburization samples, and morphology evolution of prepared iron carbide particles under CO/He (v/v=2 %/98 %) and H2/CO/He (v/v/v=8 %/2 %/90 %) gaseous environment, by excluding the possible interference from promoter components other than Cu. [ABSTRACT FROM AUTHOR]

A study of the promotional effect of potassium on the carburization behavior of a series of spray-dried precipitated Fe2O3 catalysts (100 Fe, 100 Fe/0.52 K, 100 Fe/1.54 K, and 100 Fe/2.4 K) has been performed by using in situ XRD. The average crystallite size evolution for species such as α-Fe2O3, Fe3O4, χ-Fe5C2, and θ-Fe3C were followed. The potassium promoter clearly inhibits the reduction of α-Fe2O3 to Fe3O4, where the decreasing binding energy in the Fe 2p3/2, O 1s and K 2p3/2 spectra from X-ray photoelectron spectroscopy (XPS) suggests an electron density increase in Fe and O upon potassium promotion, leading to the enhanced covalency in the Fe−O bond. In terms of crystallite size during carburization, an optimum potassium loading exists in catalyst 100 Fe/0.52 K, which shows the fastest reduction to Fe3O4 with minimum crystallite sizes of around 7 to 15 nm. Potassium has no clear effect in determining the final crystallite size of χ-Fe5C2. An arch-shaped curve in the evolution of crystallite size of the Fe3O4 intermediate was observed, which can be explained by the activation energy difference between the bidirectional steps of the outward oxygen diffusion and the inward carbon diffusion. [ABSTRACT FROM AUTHOR]