Elucidating the Promotional Effects of the Al Element on the Catalytic Performance of Al–Cs/SiO2 for Methyl Methacrylate Synthesis via One-Step Aldol Condensation

Supported Cs-based catalysts are considered as potential candidates for methyl methacrylate (MMA) synthesis via one-step aldol condensation, but they suffer from low activity. In this paper, the acid–base properties of the Cs/SiO2 catalyst were modulated by loading different amounts of the Al element. The changes in structural and physicochemical properties following Al introduction were revealed by a series of characterizations. In-depth investigation of the catalytic mechanism through in situ DRIFT combined with DFT calculations unveiled the synergistic effects between the Al and Cs components on the promotion of catalytic performance. The results showed that the presence of Al species facilitated the formation of weak and medium acid and base sites, along with the dispersion of the active Cs component, leading to an improvement of MMA yield. Additionally, the kinetic studies indicated that the addition of Al efficiently reduced the activation energy in comparison to pristine Cs/SiO2.