Accessibility and dispersion of vanadyl sites of vanadium silicate-1 nanoparticles deposited in SBA-15

Vanadium silicalite-1 (VS-1) nanoparticles dispersed onto the mesoporous walls of SBA-15 silica have characteristics different from those of the full-grown VS-1. In particular, the vanadium-binding site differs extensively. Here, we monitor the local environment of VO(2+) with different electron paramagnetic resonance (EPR) techniques to obtain information about the heterogeneity of the vanadyl sites, the effect of a calcination/reduction cycle, and the subsequent adsorption of (13)CO(2) and NH(3) to the vanadyl sites for both full-grown VS-1 and VS1-SBA15. Furthermore, two-cycle CO(2) and NH(3) adsorption experiments were performed. While the latter showed no chemisorption of CO(2) at 373 K for both materials, clear evidence was found for ligation of CO(2) to vanadyl in full-grown VS-1 by the detection of a strong (13)C hyperfine value. This strong binding was not detected for the vanadyl centers in VS1-SBA15. Chemisorption of NH(3) was detected for all samples both by two-cycle adsorption experiments and by EPR

Rapport de conjoncture CNRS 2014 Section 14 « Chimie de coordination, catalyse, interface et procédés »

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