The selective production of propene from renewable ethanol provides a promising route toward reducing the dependence of the petrochemical industry on fossil resources. However, direct ethanol-to-propene conversion involves a complex reaction network requiring the integration of ethanol dehydrogenation, C-C bond formation and selective olefin formation. In this work, we investigate how the framework Al distribution and corresponding acid properties of ZSM-5 regulate the cooperative interaction between In₂O₃ and zeolite components during ethanol-to-propene conversion. Four structurally distinct ZSM-5 zeolites were combined with In₂O₃ to establish correlations among framework Al distribution, zeolite acidity, oxide-zeolite interfacial properties, and catalytic performance.
Catalytic testing revealed a pronounced synergy between In₂O₃ and ZSM-5. Unsupported In₂O₃ generated substantial amounts of acetaldehyde and acetone but deactivated rapidly, while the parent zeolites maintained high ethanol conversion but produced broad hydrocarbon distributions. In contrast, the In₂O₃/ZSM-5 composites efficiently coupled oxygenate formation with acid-catalyzed downstream conversion. Among the physically mixed catalysts, 50% In₂O₃/[PET]-2-pm exhibited the highest propene selectivity, reaching approximately 78% at 1 h on stream. The DRIFTS results showed that ethanol is initially activated over In₂O₃ through surface ethoxide species, followed by the formation of acetaldehyde-, acetate-, and acetone-derived intermediates. Coupling with [PET]-2 strongly suppressed the accumulation of persistent carbonyl species, indicating more efficient transfer and turnover of oxygenated intermediates at the oxide-acid interface. Acetaldehyde- and acetone-feed experiments further supported a consecutive ethanol-acetaldehyde-acetone-propene reaction pathway.
Importantly, it was revealed systematic changes in the In(3d) electronic state upon coupling In₂O₃ with ZSM-5, together with an increased contribution of defect-associated oxygen species, indicating that framework Al distribution also modifies the electronic and oxygen-defect environment of interfacial InO_x. The [PET]-2-derived composite exhibited the most favourable combination of interfacial InO_x electronic structure and accessible acid functionality, promoting efficient oxygenate relay toward propene while suppressing the accumulation of less-reactive intermediates.

Bioethanol,Indium oxide,Propene,Zeolite,Tandem reaction