Microwave-Assisted One-Pot Sol-Gel Synthesis of Tungsten Silicate Microspheres with Dispersed WOx and Their Activity in Ethanol Dehydration

Abstract

This study introduces a novel microspherical W-SiO₂ heterogeneous catalyst for alcohol dehydration, prepared via an innovative microwave-assisted condensation synthesis method. The process involves the microwave-assisted preparation of a hybrid tungsten naphthalene dicarboxylate-based precursor solution, which is subsequently condensed with (3-aminopropyl)triethoxysilane in a single step—eliminating the need for separate silica support preparation, as required in conventional impregnation methods. After calcination at 550 °C, the resulting amorphous and porous microspheres contain highly dispersed tungsten species (with loadings of 2, 6, and 12 wt.%), with no crystalline WO₃ phase detected, even at the highest loading. Compared to a 12 wt.% WO₃/SiO₂ catalyst prepared via conventional impregnation, the W-SiO₂ microspheres exhibit higher catalytic activity and ethylene selectivity in ethanol dehydration at 420 °C. Notably, the 2W-SiO₂ catalyst achieved the highest initial ethylene productivity per mole of tungsten (520 mmol mmolW⁻¹ h⁻¹), maintaining 230 mmol mmolW⁻¹ h⁻¹ after 1000 minutes on stream, indicating high long-term stability. In terms of mass-specific performance, the 12W-SiO₂ catalyst reached 133 mmol g⁻¹ h⁻¹, outperforming other comparable previously reported tungsten–silica catalysts.