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Graphical abstract Morphology control of Co 2 C nanostructures via reduction process was developed for direct production of lower olefins from syngas. The structure-performance of the as-obtained Co 2 C nanoprisms and nanospheres were investigated based on kinetic study and DFT calculations. Highlights • Morphology control of Co 2 C nanostructures via reduction process was developed. • Co 2 C nanoprisms or nanospheres can be obtained by controlling the reduction process. • The structure-performance of the as-obtained Co 2 C nanoprisms and nanospheres was investigated. • Co 2 C nanoprisms possessed higher activity and lower methane selectivity than Co 2 C nanospheres. • The product distribution of Co 2 C nanoprisms deviated from the ASF law. Abstract Fischer-Tropsch to olefins (FTO) is recognized as a surface-catalyzed structure-sensitive reaction, and the catalytic performance is strongly influenced by the morphology and exposed facets of the active phase. Here we report the effect of the reduction process on the morphology of the active phase and the catalytic performance for FTO over the CoMn catalyst. For the catalysts reduced by 10% CO-300 °C, 10% H 2 -300 °C and 10% H 2 -250 °C, Co 2 C nanoprisms were formed after reaching the steady state. However, for the catalysts reduced by CO-300 °C and 10% H 2 -400 °C, Co 2 C nanospheres were found instead. Both Co 2 C nanoprisms and nanospheres were present for the spent sample reduced by 10% H 2 -350 °C. Kinetic study found Co 2 C nanospheres to possess higher activation energy, and are more sensitive to hydrogen than Co 2 C nanoprisms. Density functional theory (DFT) calculations were also performed to clarify the structure-performance relationship of Co 2 C nanostructures for syngas conversion. [ABSTRACT FROM AUTHOR]

Direct production of lower olefins (C 2 = −C 4 = : ethylene, propylene and butylene), basic carbon-based building blocks, from carbon dioxide (CO 2 ) hydrogenation is highly attractive, although the selectivity towards olefins has been too low. Here we present a series of bifunctional catalysts contained indium-zirconium composite oxides with different In:Zr atomic ratios and SAPO-34 zeolite, which can achieve a selectivity for C 2 = –C 4 = as high as 65–80% and that for C 2 –C 4 of 96% with only about 2.5% methane among the hydrocarbon products at CO 2 conversion of 15–27%. The selectivity of CO via the reverse water gas shift reaction is lower than 70%. The product distribution is completely different from that obtained via CO 2 -based Fischer-Tropsch synthesis and deviates greatly from the classical Anderson-Schulz-Flory distribution. The zirconium component plays a critical role in determining the physicochemical properties and catalytic performance of bifunctional catalysts. Catalyst characterization and density functional theory calculations demonstrate that the incorporation of a certain amount of zirconium can create more oxygen vacancy sites, stabilize the intermediates in CO 2 hydrogenation and prevent the sintering of the active nanoparticles, thus leading to significantly enhanced catalytic activity, selectivity of hydrocarbons and stability for direct CO 2 hydrogenation to lower olefins at the relatively high reaction temperature of 380 °C. [ABSTRACT FROM AUTHOR]

Abstract: A series of Cu/Zn/Al/Zr hydrotalcite-like precursors with Zr4+:(Al3++Zr4+) from 0 to 0.7 were synthesized by a co-precipitation method. X-ray diffraction and thermogravimetric measurements demonstrated that the yield of the hydrotalcite-like phase decreases with increased Zr content. The Cu/Zn/Al/Zr mixed oxides were then obtained by calcination of the hydrotalcite-like precursors and tested for methanol synthesis from CO2 hydrogenation. With increased Zr4+:(Al3++Zr4+) atomic ratio, the exposed Cu surface area and dispersion of Cu first increase until Zr4+:(Al3++Zr4+)=0.3 and then decrease. However, the total number of basic sites on catalysts increases continuously. It is also found that the CO2 conversion is related to the exposed Cu surface area and the dispersion of Cu, while the CH3OH selectivity is related to the distribution of basic sites on the catalyst surface. The incorporation of a suitable amount of Zr is beneficial for the production of methanol, and the best catalytic performance is obtained when the Zr4+:(Al3++Zr4+) atomic ratio is 0.3. [Copyright &y& Elsevier]