Alkaline Earth Metal-Doped GdFeO3 Perovskites for Sustainable Light Olefin Production from Biomass Syngas: The Interplay of Oxygen Vacancies, Acid–Base Sites, and Catalytic Performance

The catalytic conversion of biomass-derived synthesis gas via the Fischer–Tropsch route represents a promising pathway for producing high-value products from renewable resources. This study investigates iron-containing complex oxides as catalysts for the conversion of model biomass-derived syngas. Ca-, Sr-, and Ba-doped GdFeO3 catalysts were synthesized via a sol–gel route and characterized by BET N2-physisorption, X-ray diffraction, and Fourier-transform IR spectroscopy. Their acid–base properties and oxygen non-stoichiometry were also investigated. Catalytic performance was evaluated in a fixed-bed reactor in two modes: hydrogenation of pure CO and of a CO + CO2 mixture simulating biomass-derived syngas. The results indicate that Ca, Sr, and Ba doping promotes oxygen-vacancy formation and an increase in the abundance of both acidic and basic surface sites. The effect of the promoter is not uniform with respect to activity and selectivity: Ca and Ba predominantly enhance CO and COx conversion, whereas 1% Sr primarily improves the selectivity toward light olefins at moderate conversion. All promoters suppress methane formation and enhance ethylene–propylene selectivity. Correlations are established between the surface acid–base characteristics and catalytic performance of the doped samples.