Highly Stable Au@CeO2/MnOx Core-Shell Structured Catalyst for One-Step Oxidation Esterification of Methacrolein to Methyl Methacrylate

Nano-Au particles are commonly used as an active component in oxidation esterification reactions. To inhibit the agglomeration of nano-Au particles, a series of highly stable Au@CeO2/MnOx core-shell structured catalysts were synthesized using inverse microemulsion technology for the oxidative esterification to prepare methyl methacrylate (MMA). The core-shell structured catalysts were prepared by using two different surfactants (CTAB and CO-520) and adjusting the molar ratio of water to oil (.). XRD, Raman, N-2 adsorption, ICP-MS, TEM, UV-vis, FT-IR, XPS, and -H-2-TPR were applied to characterize the samples. The nano-Au particles were encapsulated by -CeO2, forming a core-shell structure confirmed with TEM. The Au@CeO2/MnOx-C-omega = 10 catalyst prepared with CTAB as the surfactant has the best activity. The Au@CeO2/MnOxC-. = 10 catalyst has the highest hydrogen consumption and -Ce3+ content, indicating that the catalyst has the strongest interaction among Ce, Au, and Mn and more active oxygen. Active oxygen is beneficial to methanol activation and hemiacetal dehydrogenation, accelerating the formation of esters. The active oxygen content, Ce3(+) content, and H-2 consumption were correlated with the catalytic performance positively. After the catalyst was reused 10 times, the activity remained unchanged and the Au nanoparticles did not agglomerate due to the core-shell structure. [GRAPHICS]

Automated summary

This study synthesized a series of highly stable Au@CeO2/MnOx core-shell structured catalysts using inverse microemulsion technology to inhibit the agglomeration of nano-Au particles in the oxidative esterification reaction. Different surfactants and water-to-oil molar ratios were used for catalyst preparation and various characterization techniques were applied. The Au nanoparticles were encapsulated by CeO2, forming a core-shell structure. The catalyst prepared with CTAB as the surfactant showed the best activity. The content of active oxygen, Ce3+, and hydrogen consumption were positively correlated with the catalytic performance. After 10 cycles of reuse, the catalyst maintained its activity and the Au nanoparticles did not agglomerate due to the core-shell structure.