Modulating CO hydrogenation activity through silane functionalization of cobalt catalysts.

Cobalt oxide (CoO) nanoparticles (NPs) were modified with different silanes (tetraethoxysilane – TEOS, triphenyl ethoxysilane – TPES, or trimethyl chlorosilane - TMCS) by dispersing the as-synthesized CoO NPs in n-hexane solutions containing the silanes. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of these silanes on the cobalt surfaces even after reduction in hydrogen (H 2) at 573 K. Modifying CoO-NPs with TEOS resulted in face-centred cubic (fcc)-cobalt phase upon reduction whereas TPES or TMCS modification induced a mixture of hexagonal close-packed (hcp)- and fcc-cobalt phases. The modification of cobalt surfaces with the silanes alters the adsorption properties of carbon monoxide (CO) on the catalytically active sites. Furthermore, temperature programmed desorption of CO (CO-TPD) showed that the amount of dissociatively adsorbed CO relative to amount of associatively adsorbed CO increases on silane-modified cobalt surfaces, which correlates with an improved rate of CO conversion in the Fischer-Tropsch CO hydrogenation. [Display omitted] • Successful modification of CoO NPs using tetraethoxysilane (TEOS), triphenyl ethoxysilane (TPES), and trimethyl chlorosilane (TMCS). • Alteration of cobalt crystalline phases upon silane modification, with TEOS inducing a face-centred cubic (fcc)-cobalt phase and TPES/TMCS leading to mixtures of hexagonal close-packed (hcp)- and fcc-cobalt phases. • Enhanced adsorption properties of carbon monoxide (CO) on silane-modified cobalt surfaces. • Improved rate of CO conversion in Fischer-Tropsch CO hydrogenation on silane-modified cobalt oxide nanoparticles. [ABSTRACT FROM AUTHOR]