Acid treated carbon nanofibers as catalytic support for heavy oil hydroprocessing

• Functionalised CNF coated with Ni decorated MoS2 slabs were prepared.
• Catalytic performance was investigated in the hydroprocessing of a vacuum residue.
• Coke formation was very low with CNF-supported catalysts.
• CNF-supported catalysts yielded results comparable to the Al2O3-supported catalyst.

The catalytic performance of functionalised CNF coated with Ni-decorated MoS2 slabs on the hydroprocessing of a Maya vacuum residue was studied and compared with a benchmark alumina-supported NiMo catalyst. NiMo/CNF catalysts were characterised by N2 adsorption, X-ray diffraction and temperature programmed reduction of sulfided species (TPR-S). It was found that thermal cracking mainly controlled the conversion of the fraction with boiling point above 450 °C (X450+), and that catalytic cracking influenced the asphaltene conversion. MoS2 slabs morphology was varied by modifying the CNF surface chemistry. The amount of coordinately unsaturated sites determined by TPR-S was related to the MoS2 slabs morphology, although its relationship with the catalytic activity was not straightforward. Higher hydrogenation activity of the CNF supported catalysts allowed to obtain relatively high metal and sulphur conversions, despite the lack of carbon surface acidity. This helped suppress coke formation, at the expense of a less deep cracking into lighter molecules. Overall, CNF-supported catalyst yielded results comparable to the Al2O3-supported catalyst, implying that they have a high potential in heavy oil hydroprocessing.

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