Synthesis and characterization of mesoporous chromium-containing silica tube molecular sieves CrMCM-41

Journal Article · Thu Apr 08 04:00:00 EDT 1999 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp984771p· OSTI ID:347521

Zhu, Z; Chang, Z; Kevan, L ^[1]

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1. Univ. of Houston, TX (United States). Dept. of Chemistry

A series of mesoporous chromium-containing silica tube molecular sieves (CrMCM-41) with variable Si/Cr ratios have been synthesized and characterized by powder X-ray diffraction (XRD), electron probe microanalysis (EPMA), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV-visible spectroscopy (UV-vis), electron spin resonance (ESR), electron spin-echo modulation (ESEM), Raman spectroscopy, {sup 29}Si magic-angle-spinning nuclear magnetic resonance (MAS NMR), and N{sub 2} adsorption measurements. XRD, EPMA, UV-vis, and ESR show that the as-synthesized CrMCM-41 materials have the MCM-41 structure and contain only atomically dispersed Cr(III), FTIR, UV-vis, and Raman reveal that Cr(VI) monochromate exists in calcined CrMCM-41. {sup 29}Si MAS NMR and N{sub 2} adsorption show that part of the chromium is incorporated into the MCM-41 structure. ESR shows that Cr(VI)-O{sub 2}{sup {minus}} exists in calcined CrMCM-41 and transforms to Cr(V) after evacuation above 150 C. The interaction of Cr(V) with O{sub 2}, CO, C{sub 2}D{sub 4}, ND{sub 3}, CD{sub 3}OH, and D{sub 2}O was studied. Cr(V) occurs at two different sites. At one site, Cr(V) coordinates with one molecule of O{sub 2}, CO, and D{sub 2}O to form square pyramidal complexes and reacts with C{sub 2}D{sub 4}, CD{sub 3}OH, and ND{sub 3} to be reduced to Cr(III). At the other site, CR(V) is inert to O{sub 2}, CO, and C{sub 2}D{sub 4} while it coordinates with two molecules of ND{sub 3} to form six-coordinated complexes and coordinates with one molecule of CD{sub 3}OH.

• OSTI ID: 347521
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 14 Vol. 103; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMIUM
COMPOSITE MATERIALS
ELECTRON MICROPROBE ANALYSIS
MICROSTRUCTURE
MOLECULAR SIEVES
SILICA
SPECTROSCOPY
SYNTHESIS
X-RAY DIFFRACTION