(314h) A Novel Route for Alkenes and Cycloalkanes Via Ethylene Oligomerization over Heterogeneous Ni-Siral Catalysts

We describe a novel route for the production of alkenes and cycloalkanes via the oligomerization of subcritical and supercritical ethylene over a novel Ni-SIRAL catalyst. We report the production of liquid products at 50, 100, and 200^oC and 40 and 65 bar operating at both single and dual reactor configurations. The screening of reaction temperature at supercritical conditions (65 bar) indicates the highest liquid yield of 41.7 wt. % at 200^oC with a single reactor. Under supercritical conditions, at 200^oC, the liquid yield increased from 41.7 to 60.8 wt. % after the addition of a second oligomerization reactor. At subcritical conditions, we obtained liquid yields of 19.3 wt. % with a single reactor and 35.9 wt. % with a dual reactor. The dual reactor configuration proved to be the better configuration for the production of cycloalkanes, with a yield of 7.3 wt. % at subcritical conditions and 8.5 wt. % at supercritical conditions. These results indicate that supercritical ethylene may not be necessary for the production of cycloalkanes. We hypothesize that supercritical ethylene promoted the formation of cycloalkanes via the dissolution of coke, which contains linear and cyclic alkanes. However, the production of cycloalkanes at subcritical conditions may point to an additional pathway involving cyclization of long-chain products on the second oligomerization reactor. This is evident when comparing the yield for cycloalkane under subcritical conditions using a single reactor, 0.6 wt. %, with the yield obtained with a dual reactor, 7.3 wt. %. Based on the results we propose a reaction pathway that agrees with the results presented in this work. The pathway involves oligomerization, isomerization, co-oligomerization, cyclization, and dissolution of cycloalkanes from coke fractions assisted by supercritical ethylene.