Gas-assisted exfoliation montmorillonite into mono-layered nanosheets for the removal of olefins from aromatics

Abstract

To date, the scalable exfoliation of the resource-rich montmorillonite (MMT) into high-quality few-layered nanosheets still remains a grand challenge. Herein, a simple, nontoxic, and efficient strategy is proposed to exfoliate layered MMT into mono-layered MMT nanosheets (MMTNS) via thermal expansion gas-assisted exfoliation method. The essence of this method is that the high temperature expands the interlayer distance while weakens the van der Waals force between interlayer of bulk MMT and then the liquid nitrogen (L-N2) penetrated the interlayers can be quickly vaporized to exfoliate the MMT. With a high mass yield of 18–20%, the prepared MMTNS has a thickness around 1.9 nm and a reasonable aspect ratio (lateral dimension of 0.5 µm-3 µm). Meanwhile, no impurities were introduced during the whole procedure. Additionally, the exfoliated MMTNS with high specific surface area (402 m2 g−1) and more exposed acid sites is further applied for the removal of trace olefins from aromatics, the result shows higher olefin conversion (76.97%) than its parent bulk phase (50.66%). The possible reaction mechanism of removing olefins from aromatics was further proposed and investigated by gas chromatography-mass spectrometry (GC–MS).