Olefin hydrogenation overview

In this chapter, an overview is presented of studies that deal with the electronic and chemical properties of Pd in bimetallic systems. We will focus on palladium for three main reasons. First, bimetallic catalysts that contain Pd or other Group-10 metals have many uses isomerization of hydrocarbons, olefin hydrogenation, CO oxidation, alcohol synthesis, acetylene trimerization, etc. [8,10,19-21]. Second, palladium is very sensitive to the formation of bimetallic bonds [22-24]. And third, there is a vast number of experimental and theoretical articles in the literature that examine the properties of Pd in bimetallic systems [14,15,19-23,25-44]. From this large volume of work, one can get a general idea of how deep is our knowledge about the basic nature of bimetallic bonding and how it affects the properties of a metal. 

Dehydrogenation of isobutane to isobutylene is highly endothermic and the reactions are conducted at high temperatures (535—650°C) so the fuel consumption is sizeable. Eor the catalytic processes, the product separation section requires a compressor to facHitate the separation of hydrogen, methane, and other light hydrocarbons from-the paraffinic raw material and the olefinic product. An exceHent overview of butylenes is avaHable (81). 

Of the three possible substrates, thiophene, benzo[ ]thiophene, and dibenzo[, thiophene, benzo[ ]thiophene is the most easily hydrogenated to the dihydro derivative this is ascribable to the more pronounced olefinic character of the C(2)-C(3) double bond in benzo[, ]thiophene as compared to that in thiophene. There is no example in the literature of the hydrogenation of dibenzothiophene either to the tetrahydro or the hexahydro stage. The hydrogenation of benzol ]thiophene is catalyzed by transition metals such as Ru, Os, Rh, and Ir. An excellent overview of homogeneous catalytic hydrogenation of thiophenic substrates has been presented recently <2004JOM (689)4277>. 

We have four goals for this chapter 1) present an overview of the steps commonly employed to study organometallic catalysis, 2) show how the principles underlying molecular mechanics methods are applied to three specific examples (stereoselectivity in asymmetric hydrogenation, olefin polymerization, and host/guest interactions in zeolites), 3) briefly illustrate the practical applications of molecular modeling to catalysts used in industry, and 4) present a limited survey of the literature to illustrate how different workers have applied molecular mechanics to the study of properties of catalysts of importance to organometallic chemists. 

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