Low-temperature liquid-phase dehydration of glycerol to acrolein based on Fe-modified ZSM-5

Efficient acrolein production at lower temperature (200 °C). • Optimal acidity identified by tuning the Si/Al ratio in ZSM-5. • Trace Fe enhanced yield 2.4 times more and improved coke resistance. • Synergistic promotion of glycerol dehydration by Brønsted and Lewis acids. The catalytic dehydration of glycerol to acrolein represents a sustainable route for biomass valorization. However, most reported systems require high temperatures or pressure, which limits energy efficiency and sustainability. Furthermore, the relationship between catalyst acidity and acrolein formation in the liquid phase remains inadequately understood. In this work, we demonstrate that nano-sized ZSM-5 zeolites enable high acrolein selectivity under notably milder conditions (200 °C, 1.2 MPa). 0.3 % Fe-modified ZSM-5 (60) catalyst exhibits an acrolein yield rate 2.4 times higher than unmodified zeolite, achieving 41.3 % glycerol yield with 84.2 % selectivity. This enhancement originates from a tailored Brønsted-Lewis acid synergy, wherein Brønsted sites steer the reaction pathway while adjacent Fe-derived Lewis sites promote the dehydration steps. This study not only provides an efficient low-temperature strategy for glycerol conversion but also clarifies the role of acid-site synergy in liquid-phase dehydration, offering a rational approach for designing durable and selective catalysts. A series of ZSM-5 catalysts with varying Si/Al ratios were synthesized via a one-pot hydrothermal method, among which ZSM-5 (60) was identified as the optimal candidate due to its appropriate Brønsted acidity. To further enhance the cycling stability, an Fe-modified ZSM-5 catalyst was constructed by the introduce of Fe, which generated additional Lewis acid sites, creating a synergistic Brønsted-Lewis acid system. In the low-temperature (200 °C) dehydration of glycerol to acrolein, the Fe/ZSM-5 (60) catalyst achieved an acrolein yield 2.4 times than that of the unmodified ZSM-5 (60), while also exhibiting significantly improved resistance to coke formation. Download: Download high-res image (323KB) Download: Download full-size image