The Chitin/Keggin-type heteropolyacid hybrid microspheres as catalyst for oxidation of methacrolein to methacrylic acid

The Chitin-CsH₃PMo₁₁VO₄₀ (Ch-CsPAV) hybrids was prepared by a facile one-pot approach and characterized by FT-IR, XRD, SEM, TG/DTA, NH₃-TPD, XPS and NMR. The performance of Ch-CsPAV as a catalyst on the oxidative transformation of methacrolein (MAL) to methacrylic acid (MAA) was studied in this study. It was found that both acidity and redox property of the precusor (CsPAV) could be regulated upon introducing chitin as a component. Specifically, the resulted Ch-CsPAV with uniform microspheres had higher amount of acidic sites, better redox active sites (VO²⁺) and improved agent (NH₄⁺), thereby rendering an improved catalytic performance in the reaction launched. Under optimized conditions, higher MAL conversion (80%) and MAA selectivity (94%) were attained in the presence of Ch-CsPAV. In addition, the reaction mechanism of the conversion of MAL to MAA was proposed by in situ FT-IR. The hybrid catalyst showed good stability by the long-term stability test.