Asphaltenes precipitated from an off-shore California crude oil were subjected to pyrolysis and hydropyrolysis, both neat and in solvents, and catalytic hydroprocessing over Co—Mo/A12O3. Reaction products were collected as gases, maltenes, residual asphaltenes, and coke, based on a solvent extraction protocol. The yield of each product fraction was determined gravimetrically, and selected fractions were further characterized by GC, GC-MS, LC-ICP, and elemental analysis. The reaction environment altered both the kinetics of asphaltene disappearance and the selectivity to the gas, maltene, and coke product fractions. For instance, the apparent first-order rate constants for asphaltene disappearance at 400 °C were between 0.025 and 0.030 min-1 for neat reactions and pyrolysis in toluene. The corresponding yields of coke were high (≈45%), and the selectivities to maltenes at 60 min were between 0.22 and 0.45. However, the rate of asphaltene disappearance for pyrolysis in tetralin and hydropyrolysis in toluene was slower (k ≈0.008 min-1), the selectivities to maltenes were much higher (e.g., ≈0.8), and the induction time for coke formation was longer. The addition of a hydrotreating catalyst provided disappearance rate constants of about 0.020 min-1 and high selectivities (≈0.8) to maltenes and yields (≈60%) of maltenes. Coke was absent, even at high asphaltene conversions. The temporal variations of the product fractions and their selectivities allowed discernment of a reaction network for asphaltene thermal and catalytic pathways.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology