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Understanding the structures and reaction mechanisms of interfacial active sites in the Fisher-Tropsch synthesis reaction is highly desirable but challenging. Herein, we show that the ZrO2-Ru interface could be engineered by loading the ZrO2 promoter onto silica-supported Ru nanoparticles (ZrRu/SiO2), achieving 7.6 times higher intrinsic activity and ~45% reduction in the apparent activation energy compared with the unpromoted Ru/SiO2 catalyst. Various characterizations and theoretical calculations reveal that the highly dispersed ZrO2 promoter strongly binds the Ru nanoparticles to form the Zr-O-Ru interfacial structure, which strengthens the hydrogen spillover effect and serves as a reservoir for active H species by forming Zr-OH* species. In particular, the formation of the Zr-O-Ru interface and presence of the hydroxyl species alter the H-assisted CO dissociation route from the formyl (HCO*) pathway to the hydroxy-methylidyne (COH*) pathway, significantly lowering the energy barrier of rate-limiting CO dissociation step and greatly increasing the reactivity. This investigation deepens our understanding of the metal-promoter interaction, and provides an effective strategy to design efficient industrial Fisher-Tropsch synthesis catalysts. Understanding the structures of interfacial active sites is crucial in heterogeneous catalysis. Here the authors demonstrate that a ZrO2-Ru interface site significantly enhances reactivity in the Fischer-Tropsch to olefins process by altering the H-assisted CO dissociation route due to the presence of hydroxy species associated with Zr-OH*. [ABSTRACT FROM AUTHOR]

Author(s): Liangshu Zhong (corresponding author) [1]; Fei Yu [1, 2]; Yunlei An [1, 2]; Yonghui Zhao [1]; Yuhan Sun (corresponding author) [1, 3]; Zhengjia Li [1, 4]; Tiejun Lin [1]; [...]

CoMn model catalysts were prepared by co-precipitation and evaluated for higher alcohol synthesis (HAS) via syngas. The selectivity to oxygenates (mainly alcohols and aldehydes) was found to be higher than 20 C% for the Na-promoted CoMn catalyst. Among the oxygenates, C 2+ and C 6+ fractions accounted for >90 wt% and ∼50 wt%, respectively. Metallic Co 0 particles and MnCO 3 were found in both Na-promoted and unpromoted CoMn catalysts after the reaction, whereas Co 2 C nanoparticles could only be observed in the spent Na-promoted catalyst. The addition of Na benefited the carbonization of cobalt and increased the selectivity to oxygenates and CO 2 . Our studies thus suggested that Co/Co 2 C were the bifunctional dual-sites for the oxygenates formation over the Na-promoted CoMn catalyst, where Co catalyzed CO dissociation and chain propagation, while Co 2 C was responsible for CO non-dissociative activation and subsequent insertion. In addition, the sole Co 2 C nanoparticles with certain exposed facets may also act as another kind of active dual-sites for oxygenates formation. [ABSTRACT FROM AUTHOR]

A series of hollow MnOx-CeO 2 mixed oxide catalysts were prepared by employing carbon as hard templates. The activity tests reveal that the catalytic performance of MnOx-CeO 2 (CS) samples are more active than that of MnOx-CeO 2 (AC) sample, indicating carbon sphere (CS) as a more effective carbon template. Among these samples, MnOx-CeO 2 (CS1) sample exhibits the best activity, for which a maximal NO conversion (∼82%) could be attained at 220 °C when GHSV = 120,000 h −1 . In addition, the NO conversion could be further improved with lower NO initial concentration or higher O 2 content. Under the simulated flue gas condition, the activity of MnOx-CeO 2 (CS1) sample is barely affected by the presence of CO 2 , but the influence of H 2 O and SO 2 couldn’t be neglected. The characterization result proves that the core-shell hollow structure has been successfully synthesized over MnOx-CeO 2 binary oxides. For the hollow MnOx-CeO 2 sample, the mesopore structures are formed and the MnOx oxides are highly dispersed on CeO 2 support. Among these samples, MnOx-CeO 2 (CS1) sample possesses the largest S BET and V total values. The result of H 2 -TPR and oxygen pulse measurement indicates that MnOx-CeO 2 (CS) samples, especially MnOx-CeO 2 (CS1) exhibits the best redox property. Moreover, more amount of high valence Mn as redox active sites and more oxygen vacancies exist in MnOx-CeO 2 (CS1) proved by XPS technique. Overall, these properties may contribute to the excellent activity. [ABSTRACT FROM AUTHOR]