Single-Step Production of Bio-Based Methyl Methacrylate from Biomass-Derived Organic Acids Using Solid Catalyst Material for Cascade Decarboxylation–Esterification Reactions

This study shows the direct chemical conversion of a widely available carbohydrate-derived itaconic acid/methanol into the methyl methacrylate (MMA) ester via cascade decarboxylation/esterification reactions has been accomplished as a first-time occurrence over solid catalysts. The state-of-the-art Pt/Al2O3 catalytic processing displayed an optimum MMA compound selectivity (38.2 mol %) in the presence of an aqueous solution mixture with an alkaline base substance. To eliminate issues associated with the utilization of precious-metal materials, corrosive water-dissolved hydroxides, and deactivation, hexaaluminate was introduced for active stable decomposition in the production of MMA. Since defined acidic/basic sites are necessary to promote intermediates, barium hexaaluminate calcium hexaaluminate and lanthanum hexaaluminate were prepared by tuning their physical properties. To shed light on reactivity, the catalysts were characterized by extensive microscopic and spectroscopic techniques. Barium hexaaluminate (BHA) was found to have the highest turnover frequency (TOF) among all tested values. Detailed experimental/structural investigations indicated that a medium-strength Brønsted/weak Lewis boundary along with peculiar layered structure, surface defects, and characteristic area are strongly correlated with the activity/stability of BHA. A plausible elementary mechanism for this step transformation was also hypothesized, detailing protonated surface-bonded reactive precursor species.