Regeneration, isomerization catalysts

Greater cycle lengths are also on the horizon. Where one-year cycle lengths between regenerations were typical for the early generations of EB isomerization catalysts, customers now expect two-year life as a minimum, and the demand for... 

The commercialized BP and UOP processes employ different dual functional platinum catalysts. The BP process was first commercialized between 1963 and 1966 the UOP process in 1959. The BP catalyst has not been modified since its commercial introduction, but the UOP catalyst system has undergone further development (24). An advantage of the BP process is that the catalyst is activated and regenerated in situ. Considering the hydroscopic nature of all the isomerization catalyst sys-... 

Peripheral equipment further purifies, meters, and preheats the hydrocarbon feed, the nitrogen used for flushing, the air for catalyst regeneration, and the hydrogen for catalyst reduction. Two preheaters are used to preheat the feed to proper reaction temperature. The heaters are programed to minimize hydrocarbon decomposition before it enters the reaction zone of the reactor. An electrically heated aluminum-bronze block serves as a heat sink which provides adequate temperature control to the catalyst bed. A second flow reactor, heated by an electric furnace and located in series with the main reactor, is an isomerization reactor that produces an equilibrium mixture of n-butenes. 

In the direct coupling reaction (Scheme 30), it is presumed that a coordinatively unsaturated 14-electron palladium(o) complex such as bis(triphenylphosphine)palladium(o) serves as the catalytically active species. An oxidative addition of the organic electrophile, RX, to the palladium catalyst generates a 16-electron palladium(n) complex A, which then participates in a transmetalation with the organotin reagent (see A—>B). After facile trans- cis isomerization (see B— C), a reductive elimination releases the primary organic product D and regenerates the catalytically active palladium ) complex. 

The transmetallation reaction involves the transfer of the organic group from an organometallic species to a Pd(II) species and produces a trails Pd(II) species. Isomerization from the trans arrangement to a cis one is necessary prior to the reductive elimination step. Reductive elimination yields the coupled product and regenerates the transition metal catalyst. Because the reductive elimination is very fast, competing reactions leading to by-products are usually not observed. 

D.Y. (2006) Isomerization of n-butane to isobutane over Pt-modified beta and ZSM-5 zeolite catalyst catalyst deactivation and regeneration. Chem. Eng. ]., 120, 83-89. 

There are two distinct types of catalysts used for Cg aromatics isomerization. These differ in the manner that EB is converted. The catalysts that are used to isomerize EB tend to have higher metal activity and larger-pore molecular sieve components capable of accommodating naphthenic species without cracking them. EB isomerization type catalysts tend to require more regular regenerations than EB dealkyla-... 

The proposed catalytic cycle for this reaction begins with the initial attack of the in situ generated thiazolylidene carbene on the epoxyaldehyde followed by intramolecular proton transfer (Scheme 28, XXXII-XXXIII). Isomerization occurs to open the epoxide forming XXXIV which undergoes a second proton transfer forming XXXV. Diastereoselective protonation provides activated carboxylate intermediate XXXVI. Nucleophilic attack of the activated carboxylate regenerates the catalyst and provides the desired P-hydroxy ester. 

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