Hydrogenation dicyclopentadiene, selective

Application Increase the value of steam cracker pyrolysis gasoline (py-gas) using conversion, distillation and selective hydrogenation processes. Pygas, the C5-C9 fraction issuing from steam crackers, is a potential source of products such as dicyclopentadiene (DCPD), isoprene, cyclopentane, benzene, toluene and xylenes. 

Since this reaction is a unimolecular example of the selective hydrogenation of an alkene mixture, the successful saturation of the less-substituted double bond should take place most readily over those catalysts that are most effective for the preferential saturation of one olefin in a mixture. Ruthenium has not been used extensively for such hydrogenations, but P-2 Ni(B) has been effective in promoting the selective hydrogenation of one of the double bonds in 46, methylene norbornene (49) (Eqn. 15.30), dicyclopentadiene (50) (Eqn. 15.31), and 2-methyl-1,5-hexadiene (51) (Eqn. 15.32).6 9,80,81... 

P-2 Nickel boride shows a remarkable ability to selectively hydrogenate the strained double bond of norbornene. Thus hydrogenation of 5-methylenenor-bornene (1) and of the endo-dicyclopentadiene (3) give essentially quantitative yields of the dihydro derivatives (2) and (4), respectively.8... 

Ni boride (obtained from sodium borohydride reduction of Ni acetate in ethanol) exhibits sensitivity to substitution on the double bond, and to strained double bonds , and hence is useful for selective half-hydrogenation of dienes. Ni boride selectively hydrogenates the strained double bond of norbonene and dicyclopentadiene. Thus, a synthesis of 13-santalene involves the selective saturation of the endocyclic double bond of 7 over Ni boride, to afford 8 in 98% yield ... 

Allylamine is formed and reacts with 1,3-propanediamine to give 2-ethylhexa-hydropyrimidine, 25, which is dehydrogenated to 24 25 is efficient for selective hydrogenation of dienes such as dicyclopentadiene ... 

The role of transition metal hydrides has been reviewed and a comparison between gas-phase, liquid-phase and electrochemical hydrogenation has appeared . Laser radiation of Fe(CO)s photocatalyses the gas phase hydrogenation of ethylene(10-70 C, 1-2.4 atm) with quantum yields up to 170 . Selective hydrogenation of dicyclopentadiene (1) to (2) without formation of (3) is achieved via the [RhCl(PPh3)3] catalysed reduction of complex (4) . The new hydride [ThHj(MegSiR2)] (R = Bu,... 

Low-temperature selective hydrogenation converts dienes to olefins, and alkyl benzenes such as styrene to ethyl benzene, in the liquid phase. Other unstable hydrocarbons, such as dicyclopentadiene, that form gums are also hydrogenated. At the same time a-olefins isomerize to higher-octane internal olefins. 

The skeletal isomerization of tetrabydrodicyclopentadiene into adamantane is an example of a very complex rearrangement diat is commercially carried out over strong Lewis acids with a hydride transfer initiator. The reaction can be catalyzed by rare earth (La, Ce, Y, Nd, Yb) exchanged faujasites (Scheme 1) in a Hj/HCl atmosphere at 25(yX3. Selectivities to adamantane of up to 50% have been reported, when a metal fimction, such as Pt, capable of catalyzing hydrogenation is added [54]. Initially acid catalyzed endo- to exo- isomerization of tetrahydro-dicyclopentadiene takes place and then a series of 1,2 alkyl shifts involving secondary and tertiary carbonium ions leads eventually to adamantane[55]. The possible mechanistic pathways of adamantane formation from tetrahydro-dicyclopentadiene are discussed in detail in ref [56]. 

While our studies for identification of the active/selective phase continues, in a parallel effort, we have conducted some experiments to assess the role of dicyclopentadiene, one of the intermediates proposed in the literature [7]. The objective behind this phase of the study was to examine the routes that originate from dicyclopentadiene and result in phthalic anhydride versus maleic anhydride formation. The catalyst used in this set of experiments was vanadium pentoxide that was pre-reduced in situ at 400 °C with hydrogen. 

Hydroformylation of 2,6-ea o-tricyclo[5.2.1.0. ]dec-8-ene afforded preferentially the ea o-aldehyde (vertral = melon carboxaldehyde) (Scheme 6.17) [88]. Alternatively, it could be obtained in the same diastereomeric ratio by selective hydroformylation of 2,6-ex o-dicyclopentadiene and final hydrogenation on a Pd/C catalyst. If necessary, the isomers can be separated via their bisulfite... 

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