The deactivation of Pt/KL catalyst during n-heptane aromatization reaction was investigated. The activity fell quickly, especially in the initial stage. The fresh, the used and the regenerated catalysts were characterized by N-2 physisorption, HADDF-STEM, TGA, UV-Raman, etc. The rapid deactivation is attributed to declined accessibility to Pt active sites because of coke deposition. GC-MS analysis revealed that the coke species are polycyclic aromatic hydrocarbons (PAHs). The dimensions of coke molecules and the coke volumes of used catalysts were estimated via DFT calculations. The variation of the contents of different coke species with reaction time implies a shape-selective transformation under micropore constraints. This, together with the XPS-determined depth profile of the coke in the used catalyst, indicates most of the coke was internally encased near the micropore openings. Quantitative evaluation concerning the influence of coke deposition on micropore volume confirms severe channel blockage by coke. (C) 2018 Elsevier Inc. All rights reserved.