Preparation of Methyl Acrylate through Catalytic Aldol Condensation over Cs/TS-1 Catalysts

It is of great importance to design heterogeneous catalysts for aldol condensation of methyl acetate and formaldehyde to realize the green and sustainable production of methyl acrylate. Herein, Cs-based heterogeneous aldol condensation catalysts via incipient wetness impregnation were optimized through enhanced interaction between supports (amorphous SiO2, silicalite-1, and TS-1) and Cs sites. By various characterization techniques such as IR–OH and 133Cs magic angle spinning NMR, it was proven that Cs/TS-1 exhibited the strongest interaction between TS-1 and Cs species with the lowest preservation of −OH groups and the largest shift toward a higher field in NMR spectra after Cs modification as well as the highly dispersed Cs sites. Correspondingly, Cs/TS-1 shows the best catalytic performance in the gas aldol condensation of methyl acetate with formaldehyde. Importantly, it is effective to verify that the better catalytic performance is closely related to the Si/Ti–O–Cs active centers rather than that of Cs2O through H2O washing. The turnover number of Cs species of the Cs/TS-1 catalyst (468.9) was much higher than that of the silicon-supported Cs catalyst (Cs/S-1, 343.3; Cs/SiO2, 211.3), and the selectivity toward methyl acetate over Cs/TS-1 (81.8%) was higher than those for Cs/S-1 (73.2%) and Cs/SiO2 (75.0%).