Spectroscopic silica support

Titanium Alkoxides Silica-supported titanium(IV) alkoxides and Ti-silicalite are industrial epoxidation catalysts [53-56] and have been applied in deperoxidation reactions [57]. Computational and EXAFS data [53, 54] as well as spectroscopic investigations on the surface species [58] have indicated that the dominant active surface species is a four-coordinate trisUoxy complex [(=SiO)3TiOH] [59] whose coordination shell expands to six-coordinate during catalysis [60]. 

Copper atoms in these catalysts may be distributed between bulk metallic particles and oxide patches associated with the silica support. However, as mentioned previously, spectroscopic evidence suggests that little if any oxidized copper is present on a 5 wt% Cu/Si02 catalyst reduced at 573 K. Furthermore, the reduction of esters and carboxylic acids is believed to occur predominantly on metallic copper (74). Accordingly, the conjecture of these analyses is that the reaction occurs on metallic copper. 

Daniell, W., H. Landes, N. E. Fouadl and H. Knozinger, Influence of pretreatment atmospheres on the nature of silica-supported Pd generated via decomposition of Pd(acac)2 an FTIR spectroscopic study of adsorbed CO , J. Mol Catal A Chemical, vol 178, Issues 1-2,23 January 2002, pp 211-8. 

Layman KA, Bussell ME (2004) Infrared spectroscopic investigation of thiophene adsorption on silica-supported nickel phosphide catalysts. J Phys Chem B 108 15791... 

In evaluating our results and conclusions in relation to the industrial catalyst(J ), an account should also be taken of the effect of the silica support, which has not been considered here and yet is likely to play a role. In fact, as shown previously( 7,1 ), the phase distribution of the (Te,Ce)0 system differs from that of the (Te,Ce)O/SiO2 system at the same activation temperature due to the dilution and interaction effect which affects the respective formation rates and stability ranges of the various phases. In fact, from x-ray diffraction data of a fresh SiO "supported active ternary phase, the formation of some Ce02 is inferred, contrary to the results of the unsupported system. For these reasons, additional spectroscopic and catalytic... 

Structure of Alloy Type Sn-Pt/Si02 Catalysts used in Low Temperature CO Oxidation. Both Mossbauer and FTIR spectroscopy provided sufficient proof of surface reconstruction during the low temperature CO oxidation. However, the above reconstruction appeared to be reversible as the reversible interconversion of PtSn Sn -I- Pt was demonstrated by both spectroscopic techniques. This reversibility can only be achieved if the segregation described above is within the supported nanoparticle, i.e., when surface reactions involved in CO oxidation do not result in formation of separate Pt and tin-oxide phases on the silica support. 

Ozensoy et al.127 also used PM-IRAS to study the CO adsorption behavior on Si02-supported Pd clusters. As mentioned above, these crystalline, ultrathin silica films possess the structural and electronic properties of the bulk analogues, but are thin enough to permit the use of vibrational and electronic spectroscopic techniques (and tunneling microscopy) without charging.39 40 As with the... 

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