CHARACTERIZATION OF SILICA CATALYST SUPPORTS BY SINGLE AND MULTIPLE-QUANTUM PROTON NMR-SPECTROSCOPY

Date

1995-03-16

Author

HWANG, SJ
Üner, Deniz
KING, TS
PRUSKI, M
GERSTEIN, BC

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

204
views

0
downloads

Cab-O-Sil HS5, used as the support in silica supported ruthenium (Ru/SiO2) catalysts, was characterized via single and multiple quantum (MQ) H-1 NMR spectroscopy. The samples were studied both in the presence and in the absence of ruthenium. Single quantum spin counting of protons on silica support with and without ruthenium metal indicated that the total number of hydroxyl groups decreased significantly with increasing reduction temperature over the range of 350-530 degrees C. Two different components shown in static H-1 NMR were found to reveal homogeneous and inhomogeneous broadening via spectral hole burning experiments. H-1 MQ-NMR spin counting, based on the number of MQ coherences observed, showed the existence of small clusters of proton spins on the silica surface. The maximum measured cluster size was 6-7, or less, spins. Segments of silica resembling the 100 face of cristobalite on the surface are postulated to be possible sites for the clusters. The clusters in pure silica became smaller as the reduction temperature increased over 500 degrees C. No such change was detected in the presence of ruthenium.

Subject Keywords

Physical and Theoretical Chemistry, General Engineering

URI

https://hdl.handle.net/11511/42622

Journal

JOURNAL OF PHYSICAL CHEMISTRY

DOI

https://doi.org/10.1021/j100011a042

Collections

Department of Chemical Engineering, Article

Suggestions

OpenMETU
Core

Development of the ReaxFF Reactive Force Field for Inherent Point Defects in the Si/Silica System Nayir, Nadire; van Duin, Adri C. T.; Erkoç, Şakir (American Chemical Society (ACS), 2019-05-16) We redeveloped the ReaxFF force field parameters for Si/O/H interactions that enable molecular dynamics (MD) simulations of Si/SiO2 interfaces and O diffusion in bulk Si at high temperatures, in particular with respect to point defect stability and migration. Our calculations show that the new force field framework (ReaxFF(present)), which was guided by the extensive quantum mechanical-based training set, describes correctly the underlying mechanism of the O-migration in Si network, namely, the diffusion of...
Structure sensitive hydrogen adsorption: Effect of Ag on Ru/SiO2 catalysts Savargaonkar, N; Narayan, RL; Pruski, M; Üner, Deniz; King, TS (Elsevier BV, 1998-08-15) The dynamics and energetics of hydrogen chemisorption on silica-supported ruthenium and ruthenium-silver bimetallic catalysts were studied by H-1 NMR spectroscopy and microcalorimetry. It was observed that the amount of hydrogen adsorbed on Ru particles having intermediate and low heats of adsorption was significantly reduced with increasing amounts of silver. The desorption and adsorption rate constants, determined from selective excitation NMR experiments, were lower on Ru-Ag catalysts than those on Ru ca...
Synthesis, characterization, and catalytic activity of supported molybdenum Schiff base complex as a magnetically recoverable nanocatalyst in epoxidation reaction Moradi-Shoeili, Zeinab; Zare, Maryam; Bagherzadeh, Mojtaba; Özkar, Saim; Akbayrak, Serdar (Informa UK Limited, 2016-01-01) A heterogeneous nanocatalyst was prepared via covalent anchoring of dioxomolybdenum(VI) Schiff base complex on core-shell structured Fe3O4@SiO2. The properties and the nature of the surface-fixed complex have been identified by a series of characterization techniques such as SEM, EDX, XRD, TGA, FT-IR, and VSM. The synthesized hybrid material was an efficient nanocatalyst for selective oxidation of olefins to corresponding epoxides with t-BuOOH in high yields and selectivity. The catalyst could be convenient...
INTRAZEOLITE TOPOTAXY - NA-23 DOUBLE-ROTATION NMR-STUDY OF TRANSITION-METAL HEXACARBONYLS AND OXIDES ENCAPSULATED IN SODIUM ZEOLITE-Y JELINEK, R; Özkar, Saim; OZIN, GA (American Chemical Society (ACS), 1992-07-01) Na-23 double-rotation NMR (DOR) provides details on site specific adsorption and anchoring interactions in intrazeolite hexacarbonylmetal(0) complexes, M{M(CO)6}-Na56Y, where M = Mo and W, and their molecular photooxidation products, n{MO3-x}-Na56Y, over the full composition range 0 < m less-than-or-equal-to 16, 0 < n less-than-or-equal-to 32 and 0 less-than-or-equal-to x less-than-or-equal-to 1. The shifts, intensities, and line shapes of the Na-23 DOR resonances carry information on the environments of th...
Enhanced solubility of siloxy-modified polyhedral oligomeric silsesquioxanes in supercritical carbon dioxide Demirtas, Cansu; Dilek Hacıhabiboğlu, Çerağ (Elsevier BV, 2019-01-01) Alkyl siloxy functionalization increases the solubility of polyhedral oligomeric silsesquioxanes (POSS) in supercritical carbon dioxide over an order of magnitude compared to its counterpart with fluoroalkyl groups. The studied component, octatrimethylsiloxy POSS also exhibits higher solubility than other previously studied POSS types with various alkyl and methacryl groups. The octatrimethylsiloxy POSS-CO2 solid-vapor equilibrium curves have been constructed at temperatures between 308 and 328 K by measuri...

Citation Formats

S. HWANG, D. Üner, T. KING, M. PRUSKI, and B. GERSTEIN, “CHARACTERIZATION OF SILICA CATALYST SUPPORTS BY SINGLE AND MULTIPLE-QUANTUM PROTON NMR-SPECTROSCOPY,” JOURNAL OF PHYSICAL CHEMISTRY, pp. 3697–3703, 1995, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/42622.