29-P-08-HMS catalysts containing transition metals or transition metal complexes

Fu, Zhengping; Yin, Dingrui; Zhao, Weixia; Chen, Y.; Guo, Junqiu; Xiong, C.; Zhang, Luxi

doi:10.1016/s0167-2991(01)81703-1

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“…When compared to mesoporous silicas including transition metals such as Ti or V, attention paid to Co-containing related materials has been relatively limited. Nevertheless, Co atoms have been incorporated (through co-condensation or impregnation procedures) in mesoporous silicas such as MCM-41, − HMS, , and SBA-1 . It is remarkable that, for a given set of precursors, cobalt loads achieved by impregnation are usually higher than those resulting from co-condensation.…”

Section: Introductionmentioning

confidence: 99%

High Cobalt Content Mesoporous Silicas

et al. 2004

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Silica-based MCM-41-like mesoporous materials with high cobalt content (∞ g Si/Co g 23) have been synthesized through a one-pot surfactant-assisted procedure from aqueous solution using a cationic surfactant (CTMABr ) cetyltrimethylammonium bromide) as structural directing agent, and starting from molecular atrane complexes of Co and Si as inorganic hydrolytic precursors. This preparative technique allows optimizing the dispersion of the Co guest species in the silica walls. The mesoporous nature of the final materials is confirmed by XRD, TEM, and N 2 adsorption-desorption isotherms. They display unimodal and relatively narrow pore size distributions, whereas their pore array evolves from ordered hexagonal (H 0 ) to wormhole-like (W) as the Co content increases. A careful spectroscopic (UV-visible and NMR) and magnetic study of these materials shows that, regardless of the Si/Co ratio, Co atoms are organized in well-dispersed, uniform CoO nanodomains (ca. 3 nm) partially embedded within the silica walls. These materials, which show superparamagnetic behavior, can be referred to as mesoporous CoO-MCM-41 nanocomposites.

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