In this work, the promotion mechanism of Ce as Fe and Ni catalyst promoter for the catalytic reforming of biomass pyrolysis volatiles was investigated. Fe–Ni–Ce/biochar catalysts were prepared and evaluated for their catalytic performance under N 2 and steam atmospheres. The yield of Fe–Ni–Ce/biochar catalyzed syngas (H 2 +CO) increased from 224.36 mL/g to 1299.14 mL/g (800 °C) with the change of N 2 to steam atmosphere. The addition of Ce can introduce a large number of oxygen vacancies to the catalyst, and the increase of oxygen vacancies reduces the reaction barrier of the tar, thus promoting the catalytic activity of the catalyst. In the N 2 atmosphere, the electron transfer of Ce 3+ ⇄ Ce 4+ during catalytic process promotes the production of Fe 2+ to ensure the catalytic activity of the catalyst. In the steam atmosphere, Ni will activate the active sites in a steam atmosphere in water molecules. The activated active sites increase the catalyst activity by cyclic reaction with the oxygen vacancies introduced by Ce, resulting in a higher catalytic capacity of Fe–Ni/biochar than Fe–Ce/biochar. To provide the theoretical basis for the preparation of efficient catalysts based on Fe and Ni.
Xiuquan Li,Zhongqing Yang,Li Zhang,Ziqiang He,Yunfei Yan,Jingyu Ran,Zukhra C. Kadirova
The catalytic reaction of ethane with CO 2 promotes the value-added conversion of natural gas and the resource utilization of greenhouse gases. In this work, the CO 2 -assisted ethane dehydrogenation reaction characteristics on Fe 1.5 Ni 0.5 /ZrO 2 (M, T, Mix) catalyst with different crystal plane structure were studied through catalyst activity test, catalytic reaction kinetics study and catalyst characterization analysis. It is found that the exposed crystal faces of the ZrO 2 -supported catalyst has a significant effect on the CO 2 -assisted ethane oxidative dehydrogenation reaction. The monoclinic phase Fe 1.5 Ni 0.5 /ZrO 2 -M catalyst exhibits the largest conversion of ethane (21.8%) and CO 2 (25.2%) and the maximum selectivity to C 2 H 4 (80.5%). Monoclinic phase of ZrO 2 selectively exposes the ( −1 1 1) and (1 1 1) low-index surfaces with higher oxygen vacancy (O v ) density and stronger metal-support interaction, which leads to the formation of more Fe x Zr 1-x O 2 structures with high catalytic activity. The reductive oxygen vacancy O v and Fe 2+ -O-Zr 3+ sites promote the activation of CO 2 through the cleavage of C=O bond to supplement O* species. The O* species on the oxidative Fe 3+ -O-Zr 4+ site are captured and combined with H* species derived from the selective cleavage of ethane C–H bond to generate H 2 O.
Supported catalysts have been extensively investigated and implemented in the industry due to their cost-effectiveness and promising catalytic performance. However, due to the general inert nature of the support itself, its role in the catalyst performance is often neglected and therefore not well understood despite the consideration of the physical properties of the support. This study applies the concept of electronic metal-support interaction (EMSI) to explore the impact of various supports on the active metals in Fe-Ni-based catalysts for the CO-selective catalytic reduction reaction. Through density functional theory calculations and several advanced characterizations, it can be confirmed that the EMSI effect can modify the valence states of active metals and foster interaction between different active metals, thereby influencing the reactant adsorption and catalyst performance greatly. These findings highlight the significant impact of the support on the chemical states of active metals, having far-reaching implications for designing and optimizing the supported industrial catalysts.
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