Co/SiO₂ Catalyst for Methoxycarbonylation of Acetylene: On Catalytic Performance and Active Species

Reppe carbonylation of acetylene is an atom-economic and non-petroleum approach to synthesize acrylic acid and acrylate esters, which are key intermediates in the textile, leather finishing, and polymer industries. In the present work, a noble metal-free Co@SiO₂ catalyst was prepared and evaluated in the methoxycarbonylation reaction of acetylene. It was discovered that pretreatment of the catalyst by different reductants (i.e., C₂H₂, CO, H₂, and syngas) greatly improved the catalytic activity, of which Co/SiO₂-H₂ demonstrated the best performance under conditions of 160 °C, 0.05 MPa C₂H₂, 4 MPa CO, and 1 h, affording a production rate of 4.38 g_MA+MP g_cat^-1 h^-1 for methyl acrylate (MA) and methyl propionate (MP) and 0.91 g_DMS g_cat^-1 h^-1 for dimethyl succinate (DMS), respectively. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and diffuse reflectance infrared Fourier transform spectra of CO adsorption (CO-DRIFTS) measurements revealed that an H₂ reduction decreased the size of the Co nanoparticles and promoted the formation of hollow architectures, leading to an increase in the metal surface area and CO adsorption on the catalyst. The hot filtration experiment confirmed that Co₂(CO)₈ was generated in situ during the reaction or at the pre-activation stage, which served as the genuine active species. Our work provides a facile and convenient approach to the in situ synthetization of Co₂(CO)₈ for a Reppe carbonylation reaction.