Catalyst deactivation during the hydrotreatment of asphaltene in an Australian brown coal liquid

Abstract

Catalyst deactivation in the repeated hydrotreatments of asphaltene in the liquid produced from an Australian brown coal was studied comparatively in single and two stage reactions, using commercial NiMo/Al 2O 3 catalyst in a batch autoclave. Although the H C (atomic ratio) and / tf a (carbon aromaticity) of the products stayed at certain values characteristic to the reaction conditions until the 7th run, the extent of denitrogenation decreased considerably depending on the reaction conditions. the decrease of denitrogenation was severe in the single-stage reaction at 430 °C for 3 h (70% in the first run to 58% in the fourth run), while that in the two-stage reaction at 390 °C for 2 h then 430° C for 2 h was much less (80% to 72%). the decrease in the single stage reaction at a lower temperature of 380 °C was very slight, although it provided only 43% removal of nitrogen in the first run. The increase in catalyst weight due to carbonaceous deposit was low in the two stage reaction (3% after the first run to 6% after the fifth run), while the increases in the single stage reactions at 380 °C and at 430 °C were from 8 to 9% and from 8 to 11%, respectively. It is suggested that the increase of the catalyst weight causes the decrease in denitrogenation.