EFFECT OF BITUMEN-DERIVED COKE ON DEACTIVATION OF AN HDM CATALYST

A large-pore hydrodemetallation catalyst was treated with anthracene (AN) or a bitumen feed (BIT) in mineral oil solvent to obtain coke levels up to 12% carbon. In some runs, carbazole was added to the AN-coking run and in others, a nickel porphyrin compound was added to the BIT-coking run. Physical properties of the coked catalysts were determined, as well as catalyst activities for hydrogenation (HYD) and for hydrodenitrogenation (HDN) using a mixture of naphthalene and indole in n-heptane. It was found that the coke produced via BIT appeared to be porous, while that from AN was non-porous. A significant enhancement in nitrogen on the catalyst over that in the bitumen feed was observed. Catalytic activities of the coked catalysts decreased with increasing coke content, with HDN activity loss being greater than HYD activity. Neither the nature of the coke precursor, nor the presence of nitrogen or nickel on the catalyst, affected the extent of deactivation. Apparent activation energies decreased with increasing coke content. The role of coke on catalyst deactivation is discussed in terms of its effect on the distribution of different catalytically active sites for the reactions.