Dehydrogenation of Isobutane into Isobutene

This tin-modified nanoparticle of platinum is totally selective for isobutene. For example, when the Sn/Pts ratio is equal to 0.85, the selectivity to isobutene reaches 

3 Selective Hydrogenolysis of Esters and Adds to Aldehydes and Alcohols 

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The concept of site isolation is important in catalysis. On metal particles one usually assumes that ensembles of metal atoms are necessary to activate bonds and to accommodate the fragments of molecules that tend to dissociate or to recombine. We present here three examples of such effects the dehydrogenation of decane into 1-decene, the dehydrogenation of isobutane into isobutene and the hydrogenolysis of acids or esters into aldehydes and alcohols. In most cases the effect of tin, present as a surface alloy, wiU be to dilute the active sites, reducing thereby the yield of competitive reactions. 

Here we present two examples of such effects, the dehydrogenation of isobutane into isobutene and the hydrogenolysis of acids or esters into aldehydes and alcohols. Usually the effect of tin, present as a surface alloy, is to dilute the active sites, thus reducing the yield of competitive reactions. 

The application of carbon membrane reactors for the dehydrogenation of cyclohexane into benzene was investigated by Itoh and Haraya. They found a higher conversion for the carbon membrane reactor comparing to the normal reactor, which was caused by the chemical reaction shifti ng to the product side due to the preferential permeation of H2. Sznejer and Sheintuch studied the dehydrogenation of isobutane to isobutene in a membrane reactor equipped... 

In some catalytic processes, it is necessary to avoid carbon-carbon bond cleavage. For example, isobutane is mainly transformed into its lower alkane homologues (hydrogenolysis products) on metal surfaces, while it can be converted more and more selectively into isobutene when the Pt catalysts contain an increasing amount of Sn (selective dehydrogenation process) [131]. 

The dehydrogenation reaction proceeds through the simultaneous elimination of the zeolitic proton and a hydride ion from the alkane molecule, giving rise to a transition state which resembles a carbenium ion plus an almost neutral H2 molecule to be formed. For the linear alkanes, the TS decomposes into an H2 molecule and the carbenium ion correspondent alkoxide. However, for the isobutane molecule the reaction follows a different path, the TS producing isobutene and H2. Most certainly the olefin elimination is flavored to the alkoxide formation due to steric effects as the t-butyl cation approaches the zeolite framework. The same mechanism is expected to be operative for other branched alkanes. 

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