Synergistic Brønsted and Lewis Acid Sites for Selective Catalytic Valorization of Isopropanol from VOC Streams

Directional catalytic transformation of volatile organic compounds (VOCs) into value-added chemicals represents a more sustainable strategy than complete mineralization, as it simultaneously mitigates environmental pollution and reduces carbon emissions. The primary challenge in achieving multifunctional olefin production from alcohol-type VOCs is the lack of mechanistic clarity, which hinders the targeted synthesis of selective catalysts. Herein, we developed W-Ti hybrid metal oxide catalysts (WTiO_x) with active Ti-O-W interfaces via a one-step hydrothermal synthesis and demonstrated their effectiveness for isopropanol conversion processes. Remarkably, WTiO_x-500 achieved 99.8% isopropanol conversion and 99.3% propylene yield at 140 °C, significantly outperforming TiO₂ (98.4% yield at 180 °C) and WO₃ (90.5% yield at 240 °C). WTiO_x-500 also displayed higher thermal stability, with isopropanol conversion and propylene yield decreasing by 1.0% and 1.6% after 35 h on-stream reaction. Although impurities (e.g., CO₂, HCl, SO₂) caused partial deactivation of WTiO_x-500, oxygen treatment regenerated the catalyst. A series of characterization techniques indicated that the controlled calcination temperature promoted the formation of an optimal Ti-O-W interface in WTiO_x-500 through W substitution into the TiO₂ lattice and WO₃-TiO₂ surface interaction, where W species effectively tuned the electronic structure. This configuration endowed WTiO_x-500 with moderate acidity of Brønsted (-OH) and Lewis (Ti⁴⁺/W⁶⁺) acid sites, which synergistically facilitated charge transfer between isopropanol and catalyst, accelerated C-O bond cleavage during dehydration. This work provides mechanistic insights into isopropanol dehydration and demonstrates a potential approach for VOC valorization.