Effect of Operating Conditions on the Coke Formation and Nickel Catalyst Performance During Cracking of Tar

Catalytic cracking of toluene as a tar model compound was carried out to investigate the effect of operating conditions on the coke formation and performance of nickel catalyst. The deactivation of catalyst depended on the quantity and nature of deposited coke, which were affected by the operating conditions, including temperature, nickel and steam concentration. The highest yield ratio of filamentous coke to the amorphous coke was 1.11 with the Ni/Al2O3 catalyst containing the highest amount of Ni examined, 20%, and heated at 700 °C without steam injection. The formation of filamentous coke maintained the catalyst activity at the first 20 min, which had less serious effect on the deactivation than the amorphous coke. Two types of coke deactivation trends were observed. Type I was associated with the deactivation by amorphous coke and type II was due to the corporate effects of amorphous and filamentous coke, which extended the life time of the catalyst.