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Primary, secondary, and tertiary silanamine sites formed on nitrided SBA-15 for base catalytic C[sbnd]C bond formation reactions

Moteki, Takahiko, Koga, Yuuki, Ogura, Masaru
Journal of catalysis 2019 v.378 pp. 131-139
aldehydes, catalysts, catalytic activity, chemical bonding, condensation reactions, imines, nitrogen, porous media, quantitative analysis, silica, temperature
The relationship between catalyst preparation conditions and resulting their catalytic properties on silica substituted nitrogen site, silanamine site, has been discussed for a long time. In this study, the contribution of each silanamine site for several CC bond formation reactions was deconvoluted via mathematical approach. A series of nitrided mesoporous silica samples was prepared at different nitridation temperature, and silanamine species were quantitatively analyzed. The samples were applied to aldol and Knoevenagel condensation reactions. The contribution of the site was in the order of primary > secondary ∼ tertiary silanamine species. This would be explained by steric effect of secondary and tertiary silanamine sites formed more internal of the pore wall. Moreover, the primary silanamine site showed two order of magnitude higher activity than other silanamine sites for the reaction involving aldehydes. This would be explained by the formation of imine species via dehydration.