Rutile-Phase Sn-Ti Mixed Oxides as Acid Catalysts for the Condensation of C-C Oxygenated Compounds in Water.

The design of new cost-effective and water-resistant acid catalysts is crucial for valorizing aqueous side-streams to increase the efficiency and competitiveness of bio-refineries in a sustainable way. In this work, Sn-Ti mixed oxides are prepared via a green and scalable co-precipitation method. This synthesis procedure allows obtaining homogeneous rutile-phase Sn-Ti mixed oxides with enhanced textural properties and a higher amount of Lewis acid sites. More importantly, the catalytic behavior of these Sn-Ti mixed oxides is investigated by using an aqueous mixture of C-C representative oxygenated compounds, closer to real industrial conditions and differing from usual individual probe molecules studies performed even in the absence of water. Catalytic experiments combined and correlated with spectroscopic measurements (i. e., XRD, TEM, FT-IR with pyridine adsorption-desorption and N adsorption) are performed to better understand the properties of different Sn-Ti catalysts. These materials show promising results in the condensation of light oxygenated compounds present in aqueous fractions. Homogeneous and robust rutile-phase structures with inherent hydrophobic characteristics turn these Sn-Ti materials into active and highly resistant catalysts capable to transform these low-value oxygenated compounds into a mixture of hydrocarbons and aromatics useful for blending with automotive fuels, especially under complex acidic aqueous environments and moderate process conditions.