Sustainable Synthesis of Single-Phase Ba3MgSi2O8 Nanoparticles Using Sporopollenin for Fructose Syrup Production: DFT and Quantitative NMR Insights on Glucose Isomerization

Abstract

Producing high fructose syrup (HFS) is essential for both the platform chemicals and food industries. While enzyme-based methods are commonly used, their limited availability has led to growing interest in alkali metal catalysts. However, a complete understanding of these catalysts’ mechanism is still needed. Traditional alkaline earth metal oxides suffer stability issues due to metal leaching from solid surfaces. While Ba₃MgSi₂O₈ (BMS) is well-studied for its phosphor nature, its use as a Lewis base catalyst has not been explored. We present a novel method for the synthesis of BMS nanoparticles and demonstrate its application as a Lewis base for glucose to fructose (GLU-FRU) isomerization. In contrast to the conventional high-temperature solid-state grinding (1225 °C) of BaCO₃, MgO, and SiO₂, we synthesized crystalline single-phase BMS nanoparticles from BaCl₂ and hydrous magnesium silicates encapsulated in sporopollenin (BMS-ES2), utilizing a coprecipitation method at 400 °C. We attained a remarkable 62% glucose conversion rate, resulting in 56% fructose yield with 90.3% selectivity at 90 °C in 60 min at 25% glucose loading in H₂O, marking the highest reported values among catalysts containing alkaline earth metals in water. Further investigation using NMR and DFT revealed a proton exchange mechanism favoring Ba(OH)₂ due to water dissociation at Ba sites over Mg sites. The catalyst displayed excellent reusability, with a minimal 2–4% yield decrease per cycle over five cycles. These results not only provide insights into sustainable synthesis methods for Ba₃MgSi₂O₈ but also illuminate its catalytic properties for base-catalyzed reactions and the proton exchange mechanism involved in GLU-FRU isomerization. Ba₃MgSi₂O₈ nanoparticles are sustainably synthesized from biomass waste and catalyze gram scale GLU-FRU conversion in water with excellent selectivity and reusability.