Synergistic effects between the pore structure and acid-base properties on the aldol condensation of methyl acetate with formaldehyde to methyl acrylate

Considered as the promising route to replace the petroleum-based propene selective oxidation process, direct vaporous aldol condensation of methyl acetate with formaldehyde to produce methyl acrylate has received broad attention. In this work, we found the synergistic effects between the mesoporous structure and acid-base properties on this transformative process over Cs/Zr-SiO 2 catalyst through systematic comprehensive characterizations and structure-activity analysis. The pore structure of SiO 2 support, as well as the acid-base properties of catalyst, can be regulated by the dosed Zr content during the kinetic control of tetraethoxysilane hydrolysis and consequential condensation. The weak acid and base sites derived from the generation of Si-O-Zr and Si-O-Cs structures in the Cs/Zr-SiO 2 -SG catalyst are linearly correlated to the methyl acetate conversion and methyl acrylate selectivity. The diffusion behavior of methyl acetate and formaldehyde confirmed by in situ DRIFTS measurements significantly is closely related to the conversion and selectivity. As a result, the 9.4Cs/2.2Zr-SiO 2 sample prepared with a modified sol-gel method has appropriate pore structure and balanced acid-base properties, which cooperatively improve the catalytic performance to 27.6% conversion and 78.2% selectivity. While the kinetic studies reveal that the reaction order of methyl acetate and formaldehyde on this optimal catalyst is respective to 1.1 and 0.9, with their activation barrier of 81.2 kJ/mol. Although the catalyst will become deactivated resulting from the deposition of amorphous aromatic and aliphatic species, it can be easily regenerated to the fresh sample after simple thermal treatment.