Applied Catalysis A: General, Vol.532, 57-64, 2017
Hydroprocessing of vacuum residues: Asphaltene characterization and solvent extraction of spent slurry catalysts and the relationships with catalyst deactivation
Two slurry phase catalysts with two different Mo/feed ratios (2.5 and 5 wt%) were evaluated for the hydroprocessing of a vacuum residue under batch conditions at different reaction times (0-5 h). Higher API, % HDS, %HDN, % Cony. 1000 degrees F+, H/C molar ratio, and lower MCR and asphaltene content were found for the products of the 5 wt% Mo case than the 2.5 wt% analog. Both catalysts showed signs of deactivation after four-to five-hours of reaction time. Asphaltene characterization of the feed and the hydroprocessed products using the solubility fraction method showed a reduced amount of all asphaltenes fractions. For the 5 wt% Mo catalyst, after 4h of reaction time only the most polar asphaltene fraction was observed in the product. Solvent extractions of organic material from spent slurry catalyst samples were carried out to obtain a better understanding of the catalyst deactivation during hydroprocessing of vacuum residues. A blend of 10% methanol in dichloromethane and pyridine was used as solvents. The results of the solvent extractions showed that the asphaltenes deposited on the 2.5 wt% Mo catalyst had a higher concentration of the less soluble asphaltenes than those observed for the 5 wt% analog. These results suggest that the fractions removed by solvent extractions could be precursors for coke formation and responsible for catalyst deactivation. A higher percentage of organic extracts was found using pyridine (37 wt%) than that obtained by using 10%MeOH/90%CH2Cl2 (33 wt%) and pyridine organic extracts were more aromatic (aromaticity and lower H/C molar ratio) and had a higher concentration of the highest solubility parameter asphaltenes. All these results contribute to a better understanding of the catalyst deactivation process on slurry phase hydroprocessing catalysts. (C) 2016 Elsevier B.V. All rights reserved.