Isomerization selectivity, supported

Changes in isomerization selectivity in the reaction of neopentane with H2 may be a convenient diagnostic parameter to determine if Pd interacts with a support. Sometimes such changes are very small, for example, the case of differently treated Pd/Al203 catalysts (204). However, in this case,... 

There is no doubt that the initial selectivity is governed by the characteristics of the oxygen at the surface. The subsequent reactions also influence the overall selectivity support acid sites catalyze the isomerization of EO giving acetaldehyde, which is very reactive towards complete combustion. The beneficial influence of alkali promoters is due to the poisoning of the acid sites at the catalyst support. 

Anderson considers hydrogenolysis reactions in detail, along with isomerization reactions, on supported metals. The model is illustrated using butane in Figure 1. The parameters used are X, the fractional conversion of reactant the isomerization selectivity, the selectivity, S, to a j-carbon-number product (C ) the ratio, T., of the desorption rate of adsorbed C. (C. ) to the rate... 

Nickel complex-containing zeolite materials Ni(MeCN)6(BF4)2/NaX and Ni(acac)2 have been prepared and characterized by X Ray photoelectron spectroscopy (XPS). These materials are catalytically active for ethylene dimerization and 1-butene isomerization. The supported systems show higher selectivity towards 1-butene formation compared with the homogeneous system. These features were attributed to a new nickel species formed in the supported systems. 

The choice of an appropriate support is of no less importance than that of active phase of a catalyst. We have focused our attention on the application of hydrophobic supports to prepare effective platinum catalysts for hydrosilylation since our preliminary experiments have shown that in a number of hydrosilylation reactions hydrophobic material-supported catalysts appeared to be superior to those based on hydrophilic supports such as alumina and silica. We have also aimed at selecting such supports which, in addition to their hydrophobicity, do not have acid centers on their surfaces, and due to this, they do not catalyze undesirable side reactions of isomerization. The supports selected for our study were styrene-divinylbenzene copolymer (SDB) and fluorinated carbon (FC), because nonfunctionalized SDB is free of acid sites and surface acidity of FC is extremely weak (H 9). The performance of SDB- and FC-supported platinum catalysts was studied in several reactions of hydrosilylation. 

Supported bimetallic Re—Pt catalysts are important in selective reforming of petroleum. It is believed that sulhding the catalyst before use gives ReS units which act as inert diluents to reduce the size of a local ensemble of platinum atoms. Selectivity for desirable dehydrocyclization and isomerization reactions... 

Selective Isomerization of Alkanes on Supported Tungsten Oxide Acids... 

Previous studies have concluded that 4-, 5-, and 6-coordinate W species are present on AI2O3 and Ti02 supports [17,30] depending on surface W density and on hydration state. The present study has detected W03-like distorted octahedral domains at all surface densities and irrespective of hydration on Zr02. These species catalyze alkane isomerization reactions with much higher turnover rate and selectivity than dispersed WOx moieties on alumina or titania. 

A series of anchored Wilkinson s catalysts were prepared by reacting the homogeneous Wilkinson catalyst with several alumina/heteropoly acid support materials. These catalysts were used to promote the hydrogenation of 1-hexene. The results were compared with those obtained using the homogeneous Wilkinson and a l%Rh/Al203 catalyst with respect to catalyst activity and stabihty as well as the reaction selectivity as measured by the amount of double bond isomerization observed. The effect which the nature of the heteropoly acid exerted on the reaction was also examined. 

A new isomerization catalyst can be prepared by the modification of silica-supported nickel with tetrabutyltin. This catalyst is capable of the selective isomerization of 3-carene to 2-carene.269... 

Further support for the proposed mechanism of hydride-catalyzed dihaptoacyl isomerization is derived from deuterium labelling studies. When the reaction is conducted with an excess of Th[(( 3)505]2 2)2 the enolate product is selectively deuterated at the H position (Figure 3b) as expected from eq.(12). Furthermore, nmr studies confirm the production of... 

---