Hydrocracking of Octacosane and Cobalt Fischer–Tropsch Wax over Nonsulfided NiMo and Pt-Based Catalysts
Hopps, Shelley D.
Davis, Burtron H.
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The effect of activation environment (N<sub>2</sub>, H<sub>2</sub> and H<sub>2</sub>S/H<sub>2</sub>) on the hydrocracking performance of a NiMo/Al catalyst was studied at 380 °C and 3.5 MPa using octacosane (C<sub>28</sub>). The catalyst physical structure and acidity were characterized by BET, XRD, SEM-EDX and FTIR techniques. The N<sub>2</sub> activation generated more active nonsulfided NiMo/Al catalyst relative to the H<sub>2</sub> or H<sub>2</sub>S activation (X<sub>C28</sub>, 70–80% versus 6–10%). For a comparison, a NiMo/Si-Al catalyst was also tested after normal H<sub>2</sub> activation and showed higher activity at the same process conditions (X<sub>C28</sub>, 81–99%). The high activity of the NiMo/Al (N<sub>2</sub> activation) and NiMo/Si-Al catalysts was mainly ascribed to a higher number of Brønsted acid sites (BAS) on the catalysts. The hydrocracking of cobalt wax using Pt/Si-Al and Pt/Al catalysts confirmed the superior activity of the Si-Al support. A double-peak product distribution occurred at C<sub>4</sub>–C<sub>6</sub> and C<sub>10</sub>–C<sub>16</sub> on all catalysts, which illustrates secondary hydrocracking and faster hydrocracking at the middle of the chain. The nonsulfided NiMo/Al and Pt/Al catalysts, and NiMo/Si-Al catalyst produced predominantly diesel (sel. 50–70%) and gasoline range (sel. > 50%) hydrocarbons, respectively, accompanied by some CH<sub>4</sub> and light hydrocarbons C<sub>2</sub>–C<sub>4</sub>. On the other hand, the hydrocarbon distribution of the Pt/Si-Al varied with conditions (i.e., diesel sel. 87–90% below 290 °C or gasoline sel. 60–70% above 290 °C accompanied by little CH<sub>4</sub>) The dependence of the isomer/paraffin ratio on chain length was studied as well. The peak iso/paraffin value was observed at C<sub>10</sub>–C<sub>13</sub> for the SiAl catalyst.
Biomedical and Chemical EngineeringMechanical Engineering