Facile Synthesis of Defective Porous Sn-Modified CeO2 Catalyst via Ball Milling-Pyrolysis Method for Efficient Conversion of Biomass-Derived Oxygenates

The conversion of biomass-derived oxygenates to sustainable chemicals and renewable fuels is a desirable path, while designing efficient catalysts is key to this process. However, efficiently exposing active sites still remains a significant challenge for improving catalytic performances. In this study, a defective porous Sn-modified CeO2 (Sn-CeO2–BM) catalyst was developed via a facile ball milling-pyrolysis strategy. It showed an excellent catalytic performance in the selective conversion of biomass-derived acetone–n-butanol–ethanol (ABE) fermentation to 4-heptanone. The conversion over Sn-CeO2–BM achieved 95% with 82% liquid selectivity of 4-heptanone, which were superior to those over other Sn-modified CeO2 via conventional synthesis methods. A combination of X-ray diffraction, thermal gravimetric analysis, N2 adsorption–desorption, Raman, X-ray photoelectron spectroscopy, pyridine IR, transmission electron microscopy, and high-angle annular dark field-scanning transmission electron microscopy provided a comprehensive understanding of its porous structure and defective properties. It was found that the Sn-CeO2–BM catalyst displayed a high surface area of 114.86 m2·g–1 with a narrow pore size distribution of 4.28 ± 2.2 nm. The Sn species were highly dispersed in the ceria lattice with no remarkable aggregation. It also showed a high oxygen vacancy concentration (1.47) from UV–Raman spectra, which was higher than those of the conventional ceria-supported Sn catalyst (0.68) and Sn-doped ceria (1.44). It was concluded that the efficiently exposed active sites of Sn species and defect sites lead to an excellent catalytic performance of Sn-CeO2–BM in the selective conversion of ABE fermentation to 4-heptanone. This work proposes a facile way to design and synthesize highly efficient porous CeO2-based catalysts.