Tuning Surface Lewis Acid-Base Synergy of In-Doped ZnAl Catalysts for Efficient Dehydration-Assisted CO₂-Glycerol...

The catalytic valorization of CO₂ and glycerol into glycerol carbonate (GC) provides a sustainable pathway for carbon management and biodiesel byproduct utilization. Herein, a series of In-doped ZnAl hydrotalcite-derived catalysts were developed for the dehydration-assisted synthesis of GC using 2-cyanopyridine. Structural characterization indicates that indium incorporation finely modulates the electronic environment of Zn and Al species, optimizing the distribution of surface Lewis acid-base sites. Moderate doping (x = 0.1) significantly enhanced the density of medium-strength basic sites crucial for CO₂ activation while suppressing the strong basicity responsible for nonselective glycerol polymerization. Under 170 °C and 4.0 MPa of CO₂, the optimal In_0.1/Zn₄Al-CHT catalyst exhibited a glycerol conversion of 70.2% and a GC selectivity of 68.8%, delivering a superior space-time yield (STY) of 6.71 mmol g_cat^-1 h^-1. Mechanistic analysis suggests that the synergistic interaction between In-induced basic sites and Lewis acid centers facilitates the selective carbonylation pathway. Furthermore, the catalyst demonstrated robust structural stability and reusability over multiple reaction cycles without significant metal migration or sintering. These findings highlight the potential of indium-doped mixed oxides as efficient, non-noble bifunctional catalysts for industrial CO₂ utilization.