Hydrogenation Reactions and Other Possibilities

In a further example of the hydrogenation of COg over composite catalysts, for instance Cu-Zn-chromite and HY zeolite/ it has been demonstrated that this combination of methanol synthesis and methanol-to-gasoline catalysts enables the direct formation of ethylene and propylene. The influence of the addition of alkaline metals, of the reaction temperature and of the space velocity on the production of alkenes shows that alkanes are obtained by hydrogenation of the corresponding alkenes. 

Many support materials have been studied, with a variation in the extent to which this interacts with the metal component. Thus, silica ° and alumina ° have been largely studied along with inert supports such as carbonaceous materials.  

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Hydrogenation Reactions and Other Possibilities Aimed to Reuse C02... 

Hydrogenation reactions and other possibilities aimed at re-using CO2. 

There are many compounds in existence which have a considerable positive enthalpy of formation. They are not made by direct union of the constituent elements in their standard states, but by some process in which the necessary energy is provided indirectly. Many known covalent hydrides (Chapter 5) are made by indirect methods (for example from other hydrides) or by supplying energy (in the form of heat or an electric discharge) to the direct reaction to dissociate the hydrogen molecules and also possibly vaporise the other element. Other known endothermic compounds include nitrogen oxide and ethyne (acetylene) all these compounds have considerable kinetic stability. 

QM/MM and full QM methodologies have been demonstrated to be accurate enough to study the enantioselectivities of specific asymmetric hydrogenation reactions and have helped to unravel the mechanistic complexity of these processes. These methods are, however, still quite expensive to cany out a complete screening of a real catalytic system where many combinatiOTis leading to different products may be possible. Other approaches such as QSAR-Uke approaches based on descriptors [47] and pure MM calculations with a specifically tailored Q2MM force field have been also productive alternatives [48,49]. 

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