Zr doped flexible TiO₂ nanofibrous membranes for high-efficiency oily particulate matter removal from high temperature flue gas

The filtration of high-temperature flue gases containing complex gas composition and oily particulate matter (PM) poses great challenges to the design of air filtration membranes. Ceramic nanofibers are potential membrane materials that possess the thermal resistance necessary for high-temperature filtration but the inherit poor brittleness limits their use. Herein, we report the fabrication of a flexible and porous Zr-doped TiO₂ nanofibrous membrane (Zr–TiO₂ NFM) for oily PM removal from high-temperature flue gas. The doping of Zr⁴⁺ ions not only improved the mechanical strength, leading to an outstanding tensile strength as high as 1.78 MPa, but also endowed a high specific area (68.34 m² g⁻¹). The prepared Zr–TiO₂ NFMs possessed a high filtration efficiency of 99.98% with low pressure drop of 96 Pa (industrial gas velocity of 1 m∙min⁻¹) and excellent long-term stability after 5 cycles of filtration at 350 °C. Significantly, different capture and evolution behaviors of PM at 25–350 °C were discovered. Below 200 °C, the oily particles would adhere, coalesce, spread out and form oil film on fibers. Different from oily particles, the non-oily particles would attach and accumulate on the fibers when temperatures are higher than 200 °C. This study brings a new insight to deeply understanding the capture process of PM at different temperatures and designing next-generation membranes for high temperature flue gas filtration.