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Ethanol steam reforming (ESR) is an attractive way to produce renewable H 2 and has been intensely studied. An iron promoted Ir catalyst IrFe/Al 2 O 3 is reported for the first time to show better performance than Ir/Al 2 O 3 in ESR and the structural change in the IrFe/Al 2 O 3 catalyst under realistic ESR conditions is investigated. IrFe alloy is observed after reduction in H 2. However, the IrFe alloy is disrupted during ESR because of an adsorption-induced structural change. Ir appears in metallic-like state while Fe exists as partially reduced Fe x O y under the reaction condition. The active center is therefore IrFe x O y instead of IrFe alloy. The discovery of the transformation of IrFe alloy to IrFe x O y during ESR deepens the understanding of the dynamic behaviour of IrFe catalyst and provides a correlation between the catalyst structure and catalytic performance. [Display omitted] • IrFe/Al 2 O 3 performances better than Ir/Al 2 O 3 for ESR. • Addition of Fe improves dispersion of Ir. • The formation of IrFe alloy and the disruption of alloy under ESR condition is first reported. • Ir-Fe x O y is proposed to be the active sites for ESR instead of IrFe alloy. [ABSTRACT FROM AUTHOR]

In this study, a series of zeolites, including small pore (SAPO–34), medium pore (Ferrierite, ZSM–5, and ZSM–11), and large pore (MOR and BETA) zeolites were explored as supports for nickel catalysts. The catalysts were prepared by the deposition–precipitation (D–P) method to obtain ca. 10 wt% Ni loading. The structures of prepared catalysts were elucidated using a wide range of characterization techniques such as BET, XRD, TEM, H 2 –TPR, NH 3 –TPD, FTIR, and XPS. It was found that 1:1 nickel phyllosilicate structures is formed over D–P nickel catalysts, while 2:1 nickel phyllosilicate was identified only over Ni/BETA catalyst. Furthermore, Ni/ZSM–5 catalyst was also prepared by impregnation method as a reference to investigate the effect of preparation method. The impact of the topological structures of zeolite on the catalytic activity of reactants (i.e., cyclic ethers derived from furanic compounds), reaction intermediates (i.e., polyols) was subsequently investigated. The ring–opening of THFA can proceed over Ni/Ni phyllosilicate species on the external surface of the catalyst, producing pentane polyols. Then, the pentane polyol intermediates can further undergo ring–closure pathway, predominantly over the internal acid sites within zeolite structures (except for Ni/SAPO–34). It was found that medium–pore zeolites (ZSM–5 and ZSM–11) with mild acidity exhibit the highest reaction rate with a THP yield up to ca. 64%. Similarly, the highest catalytic activity during THPM conversion was achieved over ZSM–5– and ZSM–11– supported nickel catalysts, with up to 51% selectivity towards 16HDO. Comparing the zeolite maximum pore sizes and the kinetic diameters of the reactants and products with the catalytic performance, it is clear that topological structures of ZSM–5 and ZSM–11 have pore confinement effect on the reaction mechanism and catalytic activity in the hydrogenolysis of cyclic ethers and polyols. [ABSTRACT FROM AUTHOR]

The Modified Fischer-Tropsch process converts CO 2 to chemicals using a dual-function Fe-based catalyst composed typically of magnetite and iron carbides. However, catalyst deactivation limits its industrial application. In this study, we combined Density Functional Theory (DFT) calculations and experiments to provide insights into the underlying catalyst deactivation and regeneration mechanisms. The dynamic state of the catalyst was observed with time on stream, revealing the impact of the evolving reaction mixture along the reactor. Rapid CO 2 and H 2 O dissociation on the carbide phase creates persistent *O, causing Fe 5 C 2 deactivation through oxidation. On the other hand, the direct carburization of Fe 3 O 4 proves challenging due to significant energy barriers, underscoring the need for metallic Fe or a highly reduced surface as a precursor to effective catalyst activation. These insights into iron catalyst evolution during CO 2 reduction can guide the development of strategies for achieving efficient catalyst performance. [Display omitted] • Evolving reaction mixture drives catalyst's phase transformation and deactivation. • Persistent *O surface species from CO 2 and H 2 O dissociation oxidize the carbide phase to Fe 3 O 4 , causing deactivation. • Direct carburization of Fe 3 O 4 faces high energy barriers, highlighting the need for reduction before regeneration. [ABSTRACT FROM AUTHOR]