Study on the deactivation mechanism of HZSM-5 in the process of catalytic cracking of n-hexane

•The strong acid sites catalyzed the growth of internal coke.•Internal coke could be selectively removed in H2 between 500 and 850 °C.•External coke with graphic structure resisted H2 treatment.•Two coking deactivation stages were observed during 200h of hexane cracking.