Catalytic dehydrogenation cyclical processes

For those reactions such as dehydrogenation of butane or isobutanc which require frequent regeneration of the catalyst or catalytic membrane, a cyclic process involving reaction and coke-bumout steps in sequence may need to be considered. It is essential, however, that a purge step be installed between the reaction and the burnout steps to... 

Several commercial processes have been developed for the catalytic dehydrogenation of propane to propylene as presented in Table 4. Of the seven commercial propane dehydrogenation plants in operation, six use UOP s Oleflex continuous moving-bed process. The other uses ABB Lummus Catofin cyclic multiple-reactor system. Other processes include Krupp Uhde s STAR process, as well as technologies from Linde and Snamprogetti. ... 

The same cycle is followed during the reactions of linear alkanes to form linear alk-enes. Although the thermod)mamics for dehydrogenation of cyclooctene are more favorable than those for the dehydrogenation of linear alkanes, primary C-H bonds typically undergo oxidative addition faster than secondary C-H bonds, as discussed in Chapter 6. Thus, linear alkanes react faster than cyclic alkanes. However, the accumulation of a-olefin inhibits the catalytic process. An T) -olefin complex formed from the a-olefin becomes the resting state of the catalytic cycle for reactions catalyzed by the POCOP system, instead of the vinyl hydride complex that is the resting state of the PCP system. The accumulation of the olefin complex that lies off the cycle leads to a lower concentration of the iridium complexes within the cycle and slower reactions as the concentration of a-olefin product increases. 

When a Pd-catalyzed dehydrogenation process is applied to WWdisubstituted hydroxylamines, the corresponding nitrones, which are valuable intermediates to construct various biologically active nitrogen compounds, are formed highly efhciently (Scheme This method will replace conventional methods, which use stoichiometric amounts of oxidants such as HgO and K3[Fe(CN)6]. " Although recently direct catalytic conversion of secondary amines to nitrones has been explored, the preparative methods of nitrones from A-hydroxylamines are limited to a few reactions. " The present Pd-catalyzed reaction is useful for the synthesis of cyclic nitrones, which cannot be obtained by the conventional method catalytically. 

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