Other Oxide Supports

The relationship of gallium oxide structure, as revealed by NMR, to catalytic activity in the conversion of methanol to diethyl ether has been investigated by 

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Early work in this area has involved the investigation of the olefin metathesis activity of [W( Bu)(CH 2Bu)J supported on silica or other oxide supports [65, 66]. While highly active, these systems do not contain a metallocarbene [40, 67]. For instance, the silica-supported system has been characterized as [ iOW( Bu)(CH 2Bu)J, and therefore it is very likely that the propagating metallocarbene is generated in situ even if it is not clear how it is formed. [ iOMo( Bu)(CH 2Bu)J also displays similar reactivity towards olefins, but is more sensitive to functional groups [67, 68]. For tantalum, despite the presence of a weU-defined metallocarbene in [( iO)Ta(=CH Bu)(CH 2Bu)J, this system is... 

Figure 15 shows infrared spectra from ethene adsorbed on a number of other oxide-supported metals [Co (217, 208, 56) Ru (50) Ir (58) Cu (52)]. 

Although UV-vis DR spectra of vanadia on other oxide supports (such as Ti02, Ce02, and Nb205) cannot be readily interpreted because of the overlap of their strong absorptions with those of vanadia, equivalent shifts of the Raman bands as a function of vanadia coverage suggest that the surface VO4 species also polymerize on these supports. 

Supporting other oxides, supporting cluster molecules For carbon oxide methanation... 

Metals such as Fe, Co, Ni, or Ru on alumina or other oxide supports convert CO and H2 to hydrocarbons. Using different catalysts and reaction conditions either CH4, liquid hydrocarbons, high molecular weight paraffins, methanol, higher alcohols, olefins, and aromatics can be obtained, though rarely (with the exception of CFL, and methanol) with high selectivity. Hydrocarbons typically exhibit a Schulz-Flory type molecular weight distribution. 

Methanation 1900s Fuels CO -b 3H2 — CH4 -b H2O Ni on AI2O3 or other oxide supports... 

V—0-Support (930cm ) and V—O—V (625 cm ) bonds. Similar distributions of monomeric and polymeric surface VO4 species are found on other oxide supports with the exception of Si02 [30]. For the supported V20s/Si02 catalyst system, only isolated surface VO4 species are present below the maximum dispersion limit (<3 V atoms/nm ). For all supported vanadium oxide catalysts, crystalline V2O5 NPs are also present above the monolayer surface coverage or maximum dispersion limit [31]. 

VII. Metal-Support Interactions In Other Oxide Supports and Related Phenomena... 

Table 7 Surface species resulting from the reaction of Ti organometallic complexes with other oxide supports...

Even though most of the supported ionic liquid catalysts prepared thus far have been based on silica or other oxide supports, a few catalysts have been reported where other support materials have been employed. One example involves a polymer-supported ionic liquid catalyst system prepared by covalent anchoring of an imidazolium compound via a linker chain to a polystyrene support [79]. Using a multi-step synthetic strategy the polymeric support (e.g. Merrifield resin among others) was modified with l-hexyl-3-methylimidazolium cations (Scheme 5.6-4) and investigated for nucleophilic substitution reactions including fluorina-tions with alkali-metal fluorides of haloalkanes and sulfonylalkanes (e.g. mesylates, tosylates and triflates). 

To understand the activity of the [W(CH3)6] (26) with other oxide supports, the synthesis was extended from silica to silica-alumina. In a similar way, like in silica, [W(CH3)6l was grafted on silica-alumina partially dehydroxylated at 500°C. Grafting experiments of [W(CH3)6] carried out in pentane at -50 to -30°C resulted in a brown solid 28 (Scheme 16). 

With respect to CH4 oxidation, the most important step was the activation of the C-H rupture. Despite theoretical calculations predicting the complete dissociation of methane over CeOg to yield CO2, from a practical point of view, ceria on its own was much less active than other transition-metal oxides. Nevertheless, the presence of ceria in noble metals or other oxide-supported systems was very beneficial. 

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