Effect of Aluminum Loading on Mesoporous Silica-Supported Catalysts for Enhanced Solketal Synthesis from Glycerol via...

The conversion of surplus glycerol from biodiesel production into solketal represents an effective strategy to enhance biofuel sustainability; however, the development of efficient and reusable solid acid catalysts with optimized acidity remains challenging. In this study, sulfated mesoporous SiO₂/Al₂O₃ catalysts with varying Si/Al ratios were synthesized and evaluated for glycerol acetalization with acetone. Process parameters were optimized using response surface methodology (RSM), considering catalyst loading, temperature, reaction time, and acetone: glycerol molar ratio. An artificial neural network (ANN) model was further developed to capture nonlinear relationships and validate predictive performance within the experimental domain. The Si/Al (50:1) catalyst exhibited excellent performance, achieving 70.0% glycerol conversion, 64.9% solketal yield, and 92.8% selectivity under the optimized conditions (7 wt % catalyst, 60 °C, 120 min, and 6:1 acetone: glycerol molar ratio). NH₃-TPD analysis revealed that this catalyst possesses a high density of moderate-strength acid sites, which are primarily responsible for its superior catalytic performance. The RSM model demonstrated high predictive accuracy, with a deviation of less than 2.2% between predicted and experimental values. The ANN model also showed strong predictive capability (overall R = 0.9962), confirming its suitability as a complementary nonlinear modeling tool within the studied range. Reusability tests indicated a gradual decline in activity while maintaining high selectivity (>87%) after four cycles. This deactivation behavior is associated with a reduction in accessible acid sites, as supported by NH₃-TPD analysis. These results demonstrate that controlled Si/Al composition effectively tunes catalyst acidity and performance, while the combined use of RSM and ANN provides a complementary modeling approach for reliable prediction within the defined experimental space, offering a practical strategy for sustainable glycerol valorization under mild conditions.