The main goal was to study the distribution and probability of chain growth of coke by the combination of Pt/SiO2 representing the metal sites with 100-120 mesh mixed with Al2O3 60-80 mesh representing the acid sites. TPO, ESR, IR and Soxhelt extraction analyzed with GC-14B were employed for coke characterization. From the effects of time, temperature, H-2/HC ratio and modification of catalysts, it was found that probability of chain growth on both sites were the same. However, the greater accumulation was occurred on the support. This offered transformation on the gas phase of coke intermediates from the metal, which was primarily responsible for producing the coke precursors. The roles H-2 and promoter was more sensitive to reduce coke and probability of chain coke, especially the effect of K promoter. (C) 2004 Elsevier B.V. All rights reserved.