Heavier Olefin Oligomerization

A light diesel fuel was produced by distillate hydrotreating of the straight-run Fe-HTFT material, while the heavier fraction was hydrocracked over a dewaxing catalyst, which produced a heavy diesel (Table 18.10). Some diesel fuel was also produced by C3-C4 olefin oligomerization over solid phosphoric acid by recycling the naphtha thus produced. It has previously been pointed out that solid phosphoric acid is not well suited for distillate production,42 and the hydrogenated... 

Figure 4 shows the reaction pathway for the isobutene oligomerization. After the dimer formation, the addition of another one butene molecule will depend mainly of Brbnsted acidity to stabilize the formation of the carbocation. The oligomerization to heavier olefins will be favored on catalyst showing a low L/B acids sites ratio [12]. 

Figures 4 and 5 show the tert-butanol TPReac results over the WZ and HY catalysts respectively. The m/e = 59 is the most important alcohol fragment The WZ catalyst is characterized by desorption with reaction to olefins almost exclusively (m/e values of 41 and 55). The ratio of masses 41 to 55 is consistent with the isobutene MS pattern throughout the whole tert-butanol TPReac spectmm over WZ. In heavier olefins (e.g., octenes), the m/e = 55 is the dominant fragment, which would have made extensive oligomerization easily detectable. On the other hand, the HY catalyst showed a richer tert-butanol TPReac pattern. Olefin oligomerization over HY was also evident by the asymmetry of the m/e 41 and 55 peaks. Note that if the two signals were only due to isobutene, we should expect them to follow exactly the same trend. However, Fig. 5 shows that m/e = 55 becomes more...

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