Bitumen Partial Upgrading Through Fixed-Bed Hydroprocessing: Examining Catalyst Stability

Bitumen partial upgrading refers to a prospective direction in the processing of Canadian bitumen where its quality is improved just enough to meet pipeline specifications. Fixed-bed hydroprocessing is an approach with the potential to achieve this objective, outside the mainstream concept of combining visbreaking and solvent deasphalting. In continuation of previous work where we examined the fitness of purpose of fixed-bed hydroprocessing to partially upgrade oil sands bitumen, in this study we investigate the stability of the hydroprocessing catalyst system when exposed to working conditions over an extended period of operation. The trial campaign was conducted in a continuous pilot plant having a fixed-bed reactor packed with a dual catalyst system. In the first part of the experimental program, conditions were scouted to find the operating window that enabled us to meet the pipeline specifications for API gravity (19 degrees API) and viscosity (350 cSt at 7 degrees C). Following completion of these tests, the stability of the catalyst over time was assessed under conditions such that the desired product quality was met. It was established that on-specification partially upgraded bitumen could be produced at conditions that permitted the attainment of residue (525 degrees C+) conversion levels of nearly 50%, with hydrogen consumption levels of 900-1000 scf/bbl. The catalyst system was stable over 1096 h of continuous operation (6.5 weeks), yielding on-specification product, but this was accompanied by a visible pressure drop buildup in the reactor. Characterization of the on-specification product showed increased yields of quality middle distillates and vacuum gas oil fractions.