K–Zr/SiO <b> ₂ </b> Catalyst for Efficient Aldol Condensation of Methyl Acetate and Formaldehyde

Cost-effective catalysts for methyl acrylate (MA) synthesis via the aldol condensation of methyl acetate (Ma) and formaldehyde (FA) remain a challenge. This study presents a series of K–Zr/SiO2 bifunctional catalysts designed by coimpregnation to achieve synergistic acid–base regulation. Characterizations (XRD, FT-IR, N2 physisorption, NH3/CO2-TPD, Py-IR, XPS) show that Zr incorporation enhances K dispersion, modulates surface acidity/basicity, and promotes the aldol condensation reaction process. The 4K-3Zr/SiO2 catalyst achieved 34.15% Ma conversion, 92.55% MA selectivity, and 2.34 mmol·gCat–1·h–1 space-time yield under optimized conditions (T = 380 °C, LHSV = 0.8 h–1, Ma:FA:MeOH = 1:2:2). Mechanistic studies show that Si–O–K and Si–O–Zr act as Lewis base and Lewis acid sites, respectively, balancing acid–base ratios and suppressing side reactions. The catalyst maintained 95% activity after four regeneration cycles, confirming its industrial feasibility. This work offers a strategy for designing cost-effective K-type catalysts in MA synthesis, highlighting the importance of acid–base synergy.