Enhanced Structural Stability and Selective Furfural Hydrogenation over Ru and Si co-doped SrFeO3-δ Perovskite

Abstract

Doping of SrFeO3-δ with transition and non-transition elements provides a powerful route to modulate its physicochemical properties. In this investigation, a series of ruthenium and silicon-codoped SrFeO3-δ (SrFe0.95-xRu0.05SixO3-δ) was prepared via the sol-gel combustion method using hexamine as fuel. The doped samples crystallized in the cubic structure with Pm-3m (221) space group. The presence of Si4+, Fe3+, Fe4+ and Ru4+ in the SrFe0.95-xRu0.05SixO3-δ sample was confirmed from XPS analysis. The presence of an EPR signal at g = 1.9393 and temperature-programmed desorption of oxygen (TPD-O2) analyses validated the presence of oxygen vacancies. The ruthenium and silicon co-doped SrFeO3-δ effectively hydrogenate biomass-derived platform molecule furfural with 95% conversion and 88% furfurylalcohol selectivity at 185 °C for 6 h using 30 bar H2 pressure. The spent ruthenium doped SrFeO3-δ (SrFe0.95Ru0.05O3-δ) catalyst exhibited a phase transformation from the cubic perovskite structure to the brownmillerite phase with exsolution of metallic ruthenium species. The exsolution of metallic ruthenium can be correlated with the formation of secondary products, viz. non-selective hydrogenation leads to formation of tetrahydrofurfurylalcohol, furan, and methylfuran. Ruthenium and silicon co-doped perovskite oxide showed selectivity towards furfurylalcohol with retention of its original cubic perovskite structure. This modification of perovskite oxide with ruthenium and silicon demonstrates a highly effective strategy for engineering stable and chemo-selective catalysts for the sustainable upgrading of platform chemicals.