Supported catalysts, for

Supported Catalysts for Propylene Polymerization. Although magnesium haUde supported titanium catalysts for propylene... 

Figure 4.28 shows an example where STM recognizes the individual metal atoms in an alloy, thus revealing highly important structural information on the atomic level. The technique does not require a vacuum, and can in principle be applied under in situ conditions (even in liquids). Unfortunately, STM only works on well-defined, planar, and conducting surfaces such as metals and semiconductors, and not on oxide-supported catalysts. For the latter surfaces, atomic force microscopy offers better perspectives. 

Bron M, Bogdanoff P, Fiechter S, Hilgendorff M, Radnik J, Dorbandt I, Schulenburg H, Tributsch HJ (2001) Carbon supported catalysts for oxygen reduction in acidic media prepared by thermolysis of Ru3(CO)i2. Electroanal Chem 517 85-94... 

Metals Dispersion from LEISS. Since He scattering Is very selective to Che outermost surface layer, one should anticipate that LEISS would be a valuable Cool for studies of metals dispersion for supported catalysts. For low oietal concentrations on high area supports, the (oietal/support) LEISS Intensity ratio should be directly proportional to metals dispersion. Recent stiidles In our laboratory have confirmed that expectation. 

X-ray diffraction has been employed for a very long time to attempt to characterize supported catalysts. For the most part, and until recently, only the width of a wide-angle peak has been employed. From the Scherrer equation, this width yields a "size". However, it has not been recognized that such a procedure faces many problems ... 

Pronkin SN, Simonov PA, Zaikovskii VI, Savinova ER. 2007. Model Pd-based bimetallic supported catalysts for nitrate electroreduction. J Mol Catal A 265 141-147. 

Table XV summarizes kinetic parameters for hydrogenolysis reactions of alkanes and cycloalkanes over film catalysts and over supported catalysts for which it can be reasonably assumed that reaction is confined to the metallic phase. These kinetic parameters refer to the overall reaction, i.e., to the rate of disappearance of the parent molecule. It will be evident from Table XV that the catalytic activity of a given metal with a given...

Some attempts to obtain a polymer-supported catalyst for chiral asymmetric allylic alkylation have been reported with some success in respect of catalyst recycling on activity, but with unsatisfactory results concerning enantioselectivity.188,189... 

The existence of two different rhodium species co-existing on the silica support can be used as an advantage by controlling their relative amount. Under standard hydroformylation conditions, the cationic species and the neutral hydride complex are both present in significant amounts. Hence hydroformylation and hydrogenation will both proceed under a CO/H2 atmosphere. Indeed a clean one-pot reaction of 1-octene to 1-nonanol was performed, using the supported catalyst for a hydroformylation-hydrogenation cascade reaction. 98 % of the 1-octene was converted in the... 

Colloidal systems were reported to be much more effective than immobilized or supported catalysts for photodegradation of ary hazardous molecule [72,73], Powdered materials exhibit an important inconvenience. The main difficulty in employing an insoluble, powdered semiconductor in aqueous dispersion is the need to remove the solids after treatment and subsequent redispersion in a second aqueous solution to be purified. However, in the case of colloids it was speculated that they may either be dispersed in the irradiated aqueous solution as a colloidal suspension, or attached to a suitable support as a fixed or mobile fluidized bed [72,73],... 

However, styrene and cyclohexene gave complex product mixtures, and 1-octene did not react under the same reaction conditions. Thus, the activity of this catalyst is intrinsically low. Jacobs and co-workers [159,160] applied Veturello s catalyst [PO WCKOj ]3- (tethered on a commercial nitrate-form resin with alkylammonium cations) to the epoxidation of allylic alcohols and terpenes. The regio- and diastereoselectivity of the parent homogeneous catalysts were preserved in the supported catalyst. For bulky alkenes, the reactivity of the POM catalyst was superior to that of Ti-based catalysts with large pore sizes such as Ti-p and Ti-MCM-48. The catalytic activity of the recycled catalyst was completely maintained after several cycles and the filtrate was catalytically inactive, indicating that the observed catalysis is truly heterogeneous in nature. 

Buchwald has shown that, in combination with palladium(II) acetate or Pd2(dba)3 [tris(dibenzylideneacetone)dipalladium], the Merrifield resin-bound electron-rich dialkylphosphinobiphenyl ligand (45) (Scheme 4.29) forms the active polymer-supported catalysts for amination and Suzuki reactions [121]. Inactivated aryl iodides, bromides, or even chlorides can be employed as substrates in these reactions. The catalyst derived from ligand (45) and a palladium source can be recycled for both amination and Suzuki reactions without addition of palladium. 

Fig. 5.5 PEG-supported catalysts for carbon-carbon bond formation. 

A Recyclable Boomerang Polymer-Supported Catalyst for Olefin Metathesis, ... 

Second Generation Recyclable Boomerang Polymer Supported Catalysts for Olefin Metathesis Application of Ardu-engo Carbene Complexes, M. Ahmed, T. Arnauld, a. G.M. Barrett, et at, Synlett 2000, 1007-1009. 

Miyadera, T. and Yoshida, K. Alumina-supported catalysts for the selective reduetion of nitric oxide by propene. Chem. Lett., 1993, Volume 22,1483-1486. 

Intermediate for the preparation of vinyloxazolines for stereoselective nitrile oxide cycloaddition Intermediate for polymer 225 supported catalyst for asymmetric allylic alkylation... 

Hoveyda and co-workers immobilized an olefin metathesis catalyst on monolithic sol-gel and claimed that the catalytic material is easily recyclable. Barrett and co-workersprepared a recyclable boomerang polymer supported catalyst for olefin methathesis by grafting the preformed catalyst to a polystyrene... 

Due to the heterogeneity of the recently advanced solid-support catalyst for the hydroformylation, direct structural information on catalyst surface has been collected by extended X-ray absorption fine structure (EXAFS). Iwasawa is the first to directly characterize the structure of dimeric rhodium complexes supported on... 

Table 8. Activities of Silica Gel and Alumina-Supported Catalysts for the Reaction of 1-Bromobutane with Aqueous KI118)...

Similar surface-supported amides have been derived from the Sm" amide Sm N-(SiHMe)2 2(thf)x by grafting on MCM-41, MCM-48 or AS-200 further elaboration led to the formation of the corresponding Sm-fluorenone ketyl, which was shown to contain surface-confined ketyl radicals.Treatment of Sm N(SiHMe2)2 (thf)x MCM-41 with MeOH, AlHBu 2 or Si(H)Me2-substituted indene gave surface-supported catalysts for methyl methacrylate polymerisation. 

---