Abstract
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•Supercritical water suppresses coke formation on ZSM-5 used for dodecane cracking.•Both catalyst modification and direct chemical participation in the coke formation reaction network are implicated.•Coke formed in the presence of supercritical water is less de-activating than coke formed in the presence.
Coking behavior of ZSM-5 was studied in the absence and presence of supercritical water (SCW) using dodecane cracking as a model reaction. SCW suppresses coke formation and inhibits conversion of coke precursors into polycyclic aromatic hydrocarbons. Interestingly, the thermal and structural characteristics of coke formed in the presence and absence of SCW appear to follow similar reaction trajectories, with the primary difference being rate inhibition in the presence of SCW. Further experiments indicated that SCW must suppress coke by an indirect role of catalyst modification and by a direct role involving chemical or physical participation in the coke formation mechanism. These results provide new insight into the role of SCW on coke formation and motivate future work to identify strategies for stabilizing acid sites in the presence of liquid water.
