Heteropolyacid hosted to nano-silica catalyst for the oxidation of methacrolein

Abstract

In this study, a catalyst was synthesized using a two-step in-situ molecular beam epitaxy method to grow H₄PMo₁₁VO₄₀ (HPAV) on amination-treated SiO₂ nanoparticles, which served as both dopant and host agents. SiO₂ dopant was modified with (3-aminopropyl)triethoxysilane (APTS), facilitating the formation of ammonium ions that enhanced the overall positive charge. This modification enabled the effective dispersion and exposure of HPAV's active species and induced a structural transformation of HPAV from a triclinic to a cubic crystal phase. The two-step hosting growth process optimized the proportions of Cs⁺, H⁺ and NH₄⁺ antinuclear ions, thereby fine-tuning the synergistic catalysis of oxidation and acidity, as well as the oxidative sensitivity at HPAV catalytic interface. The resultant 8(HPAV)&4(Cs₃PAV)-NH₂-SiO₂ catalyst achieved a methacrolein (MAL) conversion rate of 84% and a methacrylic acid (MAA) selectivity of 71%. Even after 10.5 h of reaction time, the catalyst retained its high dispersion, cubic crystal structure, and Keggin configuration, demonstrating stable catalytic performance over a continuous 200-h reaction period.