Isomerization of 1 -Hexene

Isomerization is much faster than hydrogenation on microcrystalline chromia prepared by activating in hydrogen to 400°. This may be seen 

After activation at 300°, the trans/cis ratio in 2-hexene at 35% hydrogenation is about 2, as shown in Table IV. The ratio was less for most 

Most of the experiments with 1-hexene were run to assess the effect of conditions of activation upon the rate of hydrogenation. We ran some experiments with mws-2-hexene and 4-methyl-1-pentene primarily for information about the nature of isomerization. Both compounds were obtained from the Chemical Samples Company, Columbus, Ohio. The 4-methyl-1-pentene could be used directly but poisons in the /raws-2-hexene required it to be percolated through alumina directly into the saturator. 

Results with rans-2-hexene are shown in Table VI. As with 1-hexene, chromia activated in helium at 400° gave much more hydrogenation than isomerization see runs 264 and 276. In run 276, total isomerization is about 0.3 that of hydrogenation and cis-trans isomerization is about 

Reactions between Hydrogen and trans-2-Hexene at 69° on Chromia Activated at 400° 

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Isomerization of 1-hexene to internal isomers Pt/y-Al203 Increased activity Selectivity enhancement Longer catalyst lifetime Subramaniam and McHugh (1986) Saim and Subramaniam (1990) Baptist-Nguyen and Subramaniam (1992) McCoy and Subramaniam (1995) Ginosar and Subramaniam (1995) Clark and Subramaniam (1996)... 

Supercritical fluid extraction can be used to remove carbonaceous material from spent catalysts. De Filippi and Robey (2) used supercritical carbon dioxide extraction to regenerate adsorbents. Abel (3) tried supercritical carbon dioxide extraction to regenerate a certain catalyst. Tiltscher et al. (4,5) studied the isomerization of 1-hexene on an alumina catalyst and showed that under supercritical conditions, 1-hexene was able to remove the oligomeric compounds (C -C q) from t ie catalyst surface and prevent coking. 

The double bond isomerization of 1-hexene to form 2-hexene was studied in a laboratory reactor containing rhodium particles supported on alumina at 150°C and atmospheric... 

The second example Involves alumina-catalyzed isomerization of 1-hexene. In this case however, the reaction mixture Itself is... 

Isomerization of 1-hexene. Figure 6 shows simulated equilibrium yields and conversions of 1-hexene versus temperature at the specified pressure. Cracking products were not considered in our analysis. Increase in temperature is seen to cause a slight decrease in equilibrium conversion and to have little effect on the isomer selectivities. Simulated equilibrium conversion at 250 C and 7,250 psia is 97.2%. This value compares with the experimental value of 40% obtained by Tiltsher et al. (16) in a catalytic flow reactor. Clearly, there is room for improving the experimentally reported conversion. 

In order to study the effect of SCF operating conditions on reaction equilibrium and kinetics, an experimental facility has recently been completed and successfully tested as described in the following section. The heterogeneous catalytic isomerization of 1-hexene over Pt/ y-Al20o catalyst is chosen as the model reaction system i.e., a reaction system that undergoes simultaneous deactivation by coking. 

This paper presents results from initial experimental investigations of the isomerization of 1-hexene over a commercial Engelhard reforming catalyst. Both batch and continuous runs were performed. The objective of the batch run is to compare experimentally obtained equilibium conversion and product selectivlties with those obtained through our theoretical procedure. The continuous runs were performed to compare reaction behavior at subcritical and supercritical conditions and to verify if continuous maintenance of catalyst activity is Indeed possible at dense supercritical conditions. 

Figure 8. Isomerization of 1-hexene over Pt/7-alumina catalyst in a CSTR at subcritical conditions.

As discussed earlier, transfer of deuterium to organic reactant was observed when 2,3-dimethylbutene-1 was contacted with a synthetic partially deuterated decationated Y zeolite (DHY). From Table XIV, it is seen that such HY catalysts have appreciable catalytic activity for isomerization even at extremely lowtemperatures. Transferof deuterium to olefinic reactant was associated with a decrease in the intensity of the catalyst 0—D band near 2620 cm". Similar patterns of deuterium transfer accompanied the isomerization of 1-hexene over DHY at 25°. 

Fig. 15. The isomerization of 1-hexene during its hydrogenation in the liquid phase over Adams platinum [14). Q—H %—Dj.

Figure 11.8 Effect of unwanted oligomeric by-products formed during the catalytic isomerization of 1-hexene (Tilscher, Wolf, and Schelchshorn, 1981) (1.01325 bar per atm).

A number of studies have examined alkene hydrogenation catalyzed by Ru3(CO)i2 and substituted derivatives, many reported prior to 1993. One study reported that Ru3(CO)i2 and Ru3(CO)9(PPh3)3 were catalyst precursors for hydrogenation and isomerization of 1-hexene at 303-363 K. After the hydrogenations, the IR spectra of the solutions showed H4Ru4(CO)i2 and H4Ru4(CO)i2 (PPh3) ( =1—4), respectively. In addition to hexane, the isomerization products were to r-2-hexene (up to 61%), m-2-hexene (up to 23%), and /ra r-3-hexene (up to 20%). ... 

The anion [HCrFe(CO)9] catalyzes the isomerization of 1-hexene and allylbenzene into internal olefins in the presence of light. Allylbenzene was converted into cis-and rrans-propenylbenzene. ... 

The isomerization of 1-hexene to cis- and tra 5-2-hexene was performed with [RuAu( M-H)2(CO)(PPh3)4](PF6)J l Isomerization of 1-pentene was studied in the presence of [H3Ru4 Au(PPh3) (CO)i2] and [H2Ru4 Au(PPh3) 2(CO)i2]. These two clusters are clearly more active for 1-pentene isomerization than the parent [H4Ru4(CO)i2], in marked contrast to the behavior of the ruthenium-copper analogs. 

S. Pariente, P. Trens, F Fajula, F Di Renzo, N. Tanchoux, Heterogeneous catalysis and confinement effects the isomerization of 1-hexene on MCM-41 materials, Appl Catal A, 2006, 307, 51-57. 

Diphenylphosphinated poly((aryloxy)phosphazenes) such as 10 have been shown by Allcock to be generally useful as polymeric phosphine ligands for complexing transition metals (54). Osmium complexes of 10 were found to catalyze the isomerization of 1-hexene to 2-hexene. The products in this case were separated from the catalyst by vacuum transfer. Catalytic activity ceased after [HOso(l-hexene)(CO)j (j(phosphine)] formed. 

The isomerization of 1-hexene decreased with increased ruthenium loading as shown in Table 2. It is considered that with the increased active site number on the catalyst surface, CO adsorption improved, contributing to CO insert reaction and inhibiting the isomerization of 1-hexene. The formation of oxygenate increased with increasing Ru loading, see Table 2. 

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